Since nobody has entered in a summary for United As One on the page, here's something I will give the admins so they can add it (SPOILERS AHEAD! YOU'VE BEEN WARNED!) The book starts with a prologue, which is a dream constructed by Setrákus Ra. The first one is of Marina seeing Setrákus Ra disguised as Eight, and after being rejected by Marina, he tells her that all that will come to her is pain. The second is of Five, who is in a cell, seeing Setrákus Ra offering him a second chance for the Mogadorians, which Five quickly rejects. The third is of Mark James, with Setrákus Ra telling him that he's sorry for Sarah's death, but he can bring her back, only if Mark will help him.
Number Four's narration opens up at least a day after Sarah Hart's death. John, Sam, Daniela, Nine, Walker, and her agents from New York have met up with General Clarence Lawson, the current Chairman of the Joint Chiefs of Staff, and they have spent a night at a Safehouse bunker south of Detroit called Patience Creek. Malcolm, Walker's agents from Ashwood, and the five Chimærae, as well as dozens of marines and a handful of scientists, are with them, and Number Five is in a cell. While John starts to master Invisibility and Stone Gaze, the two Legacies he has so far learned through Ximic, he continues to mourn Sarah. John overhears Sam and Daniela talk about helping him. After Nine arrives, John says that he's done grieving for Sarah. He says from this day forward, they will kill until they win.
Meanwhile, Six, Lexa, Ella, Adam and Mark, along with BK, Dust, a wounded Marina, and Sarah's body, make it away from the Skimmers and the Anubis in the Loric Ship. Six dreams about killing Setrákus Ra, reliving the battle for the Sanctuary, and Lexa wakes her up. After Six and Lexa talk about the fact that Six had to do what was necessary, Six goes back. She sees Mark, who is sleeping alongside Sarah's body. Six talks to Adam, who had been looking over Marina, who is alive, but unconscious. After Six and Adam talk, the ship arrives at Patience Creek, and the groups are reunited. Sam hugs Six, Adam and Malcolm take Marina on a gurney before John heals her, before John tells Six that he doesn't blame her for Sarah's death, but he instead only blames Setrákus Ra and himself. Ella reluctantly tells Six that Setrákus Ra is still alive.
John comes up to see Sarah's body. He says goodbye, holds her hand, and gives her one last kiss. John does not cry, but feels empty inside while saying goodbye to Sarah. Mark, who had stayed on the ship with Sarah, is disappointed that John can't resurrect Sarah. Mark yells at John, blaming him for Sarah's death on the basis that had John not fallen in love with Sarah back in Paradise, none of this would have happened. John tells Mark that he's right, but he doesn't care what Mark wants. Mark punches John, and John barely feels it. After Mark stops himself from punching John again, John tells Mark that he wants him to take Sarah home to Paradise and bury her. John then thanks Mark, and leaves the ship before Mark is sent off to take Sarah home to Paradise.
A few hours later, Six wakes up to Sam in a room. Apparently she broke down after Ella told her that Six failed to kill Setrákus Ra, and Sam got her to his room and encouraged her to take a shower. While Six gets dressed, she shares a moment with Sam. They are interrupted by military academy twins Caleb and Christian, both of which are Human-Garde (addressed by Sam as Legacy-Afflicted Native Earthlings, or LANEs). They call them to a meeting. While they prepare to go, Sam gains a new Legacy, where he has total control over technology.
Caleb and Christian lead Six and Sam, as well as Malcolm, to the meeting. Lawson, John, Nine, Ella, Lexa, Walker, and Daniela are also there. Daniela introduces herself to Six. As the meeting starts, Six wonders where Adam and Mark are, before Lawson discusses strategy with them, including whether they should hit the Warships or the Mogadorian Mountain Base in West Virginia. John is about to tell Lawson what to do when Adam is brought in. He is held prisoner by Lawson's men.
John, Six, and Nine are quick to their feet when the see Adam, and they yell at Lawson that Adam is their friend. John uses his Lumen to break Adam free of his chains. Lawson then discusses with the group about recruiting Human-Garde, or LANEs (Legacy-Afflicted Native Earthlings), as Lawson calls them, and assassinating Setrákus Ra. Lexa points out that the Mogadorians are not trying to wipe out humanity to nothing, unlike Lorien. After Lawson reveals that they have safely put many foreign Human-Garde into protective custody, John proposes that they steal Mogadorian cloaking devices to take their Warships. Lawson agrees.
After a run through of what to do, John talks to Adam, asking him if he's all right. Adam reveals that if and when Setrákus Ra dies, he will not know what will happen to his race. After a heartfelt talk, Adam takes John down to the basement of Patience Creek, where they meet Agent Noto, Walker's partner. Adam had been helping Noto with Mogadorian language. Noto had been intercepting communications from the Warships, and most of it is just white noise. The three of them suddenly get word of a video posted online.
Six and the others watch a video posted online about four Human-Garde at Niagara Falls. They are a British punk named Nigel Rally, a German boy named Bertrand, a blonde French girl named Fleur, and a Japanese girl named Ran who doesn't speak English. They used a Loralite stone to teleport themselves there. Six, Sam, Daniela, Lexa, Ella, and two of the Chimærae (Regal and Bandit) decide to go to Niagara Falls to recruit these Human-Garde. They pilot the Loric Ship out, but not before Caleb and Christian notice them, and presumably notify Lawson. As Lexa starts to pilot the Loric ship, Daniela and Ella meet officially for the first time. As Sam starts to test his Technopathy Legacy on an old game boy, he accidentally powers the ship down as its flying.
Meanwhile, John and Nine go to Five's cell in Patience Creek. John asks Five to teach him how to fly through Ximic. After Five tells John that Setrákus Ra showed up in his dream, Five begrudgingly tells John how to fly. It fails, then Five breaks through his cell and attacks John. The two fight through Patience Creek, and as they fight, John attempts to use Daniela's Stone Gaze to freeze Five, but then he realizes that he is learning to fly. After all is settled, Marina appears out of nowhere, and threatens to take Five's other eye with an icicle.
As Six and the others are about to crash the Loric Ship, Sam, with help from Ella, manages to evade disaster by turning the Loric Ship back on. They make it to Niagara Falls, and discover three destroyed Skimmers and Mogadorian ash everywhere. They see that the Human-Garde have been busy, and the Mogs took casualties. They also suddenly see a fourth Skimmer that is crashing due to a swarm of thousands of insects surrounding it, courtesy of Bertrand, who has a Legacy that allows him to control insects. They are attacked by Ran, who has a Legacy that allows her to turn any inanimate object into a grenade. Daniela stops the first bomb with her Stone Gaze. Nigel then calms Ran down, and the groups meet with them, Bertrand, and Fleur.
John tries to persuade Marina to calm down. As John explains the situation to Marina, she cautiously lowers the icicle. After Five is escorted back to his cell, Marina informs John about Setrákus Ra showing up in her dream. John tells Marina that Sarah didn't make it, and Marina hugs John. They talk a bit about how the future doesn't matter. All that does is killing Setrákus Ra and ending this war.
On their way back to Patience Creek, Ella uses her power to disable the Loralite stone so the Mogs can't get to it. Daniela tends the wounds of Fleur and Bertrand, who both suffered several blaster wounds. Six and Ella discuss about how these new recruits, with the possible exception of Ran, won't be able to help too much, as they've only had hours of experience. Sam helps Lexa land the ship at Patience Creek.
John bumps into Walker, and she talks with John about the fact that because she was MogPro, Lawson will never trust her. After telling Walker that he trusts her, John then goes with Nine and Marina to meet the returning group from Niagara Falls. John, Six, and Nine decide to train the Human-Garde. After they bring them into Patience Creek, John and Ella talk about the inevitability of all of them dying. John decides to take on a Warship, after gaining Telepathy and Dreynen through Ximic, thanks to Ella. Ella also reveals that she foresaw Sarah's death before she died, and John is angry at her, but holds himself back.
Six, John, and Marina start to plan an attack on the Toronto Warship that is over Niagara Falls with Lawson. Afterwards, Lawson talks with them how many people might die if the Mogs do invade, and also reveals that Russia turned in all their Human-Garde. Lawson also tells them that he just wishes to protect the world at all costs, and supports them. Suddenly, Agent Noto alerts them that Trueborn Commander Phiri Dun-Ra is rallying all the Trueborn Mogs, and she is telling them that they are extracting Legacies from many Human-Garde that have been captured in North America, killing them. They are then giving the extracted Legacies to Trueborn Mogs. Adam, with help from Agent Noto, quickly joins the broadcast, and he tells all the Trueborn Mogs the truth that Setrákus Ra is a Loric and a Liar. This causes massive civil unrest in the Mogadorian ranks, and the group waits for them to kill each other.
As the Mogadorian civil war begins, Sydney is destroyed with minimal casualties. The Warships over Moscow and Berlin destroy each other. The Warship over Beijing temporarily calls back all the troops. The Warship over São Paulo leaves the atmosphere. Trueborn Mogs elsewhere are joining Phiri Dun-Ra for the Mogadorian cause. John gets some sleep after advice from Lawson, but enters a vision where he and all his friends- and Sarah- are tortured in the West Virginia base. Setrákus Ra tells John in the vision that he reminds him so much of Pittacus, and tells him that he plans to replace the Mogadorians with humans when he is done taking over earth. John wakes up, and decides to end this.
Six meets Sam, who had been using his Technopathy to help Malcolm and the team of scientists to make their cloaking devices transfer data onto ordinary objects, like cell phones. Six then joins Nine, and helps him train Nigel, Bertrand, Fleur, Ran, Daniela, Caleb and Christian. Nine gives them a training exercise on their telekinesis and other Legacies. John, Adam, Marina, Ella, and Lexa, as well as BK and Dust, join the group as they are about to go to the Toronto Warship and take the cloaking devices. John tells the Human-Garde, including Sam, to stay back.
On their way to Niagara Falls, John tells the group that only him, Six, and Adam, as well as BK and Dust, will go on the Warship's hangar to get the Skimmer cloaking devices and hijack the Warship, while Marina, Nine, Ella and Lexa stay behind as backup. John carries Six and Adam, turning them invisible, and they fly up to the Warship. They are nearly spotted, but make it through the force field with help from Sam's cell phone that now doubles as a force field cloaking device, thanks to Sam's Technopathy.
John, Six, Adam, BK, and Dust sneak their way into the hangar of the Warship. After accidentally setting off the alarm, John, with help from BK and Dust, burn down the sleeping quarters of the Warship, killing hundreds of Mogadorians, while Six and Adam go elsewhere to take the cloaking devices from the Skimmers. John gains Marina's Ice Manipulation through Ximic, and goes to a training section of the Warship and kills hundreds of Mogadorians with BK and Dust. John, BK, and Dust continue to barrel through hundreds of Mogadorians until they get to the bridge.
Six and Adam worry about John psychologically, as they remove the cloaking devices from the Skimmers in the Warship hangar. John then arrives with BK and Dust, and they regroup so they can continue the attack. After Six and John blow up a big chunk of the Mogs with a fuel tank, they fight their way to the bridge, and kill all of the Trueborn there except the captain. The captain is quickly betrayed and killed by another Mog named Rexicus Saturnus, who surrenders at their mercy.
Rexicus (or Rex for short), who the Garde learn is the Mog who helped Adam rescue the Chimærae, joins the group, and they reluctantly let him in. Nine and John debate about how Rex might be a double agent, but Ella tells them that Rex has no intentions of betraying the group. They hijack the Warship, and kill every Mog in there. Ella reactivates the Loralite stone near Niagara Falls. As Adam and Rex pilot the Warship, John talks to Lawson on the phone and discusses strategy. John, thinking he can end this, decides to go take the Warship in Chicago, and flies away from the others without telling them. John makes a stop at Patience Creek to get a cloaking device, but then sees all of Lawson's guards missing. He sees Mark James, who had seemingly returned from his mission to take Sarah's body back to Paradise. Unfortunately, he was captured by Phiri Dun-Ra, dozens of Vatborn, and three Trueborn Mogs that were given Legacy Augmentations by Setrákus Ra. Phiri Dun-Ra now has an oily appendage where her left arm should be that shoots out sharp tentacles that can take Legacies for her own. The other three are a Mog with Mind Control named Thin Mog, a Mog that teleports named Shadow Mog, and a Piken-Mog hybrid. Phiri uses these tentacles to impale John through the back and take his Legacies. Mark is forced by Thin Mog to take the Voron noose that Pittacus Lore used to hang Setrákus Ra, and wrap it around John's neck. The Mogs then start killing all of Walker's agents and Lawson's soldiers.
After Six and the others are appalled at what John did, they make a quick call to Sam and with help from him and Rex they test the cloaking device on a jeep, and it works. After they tell Sam that it works, Sam tells them them that Patience Creek is under attack.
John is forced to let Phiri Dun-Ra and the Mogs into Patience Creek. Mark attempts to break free of Thin Mog's control over him and fails. Phiri then uses one of her tentacles, sharpens it, and kills Mark with it by impaling the tentacle through his head. John is powerless as Mark is killed. John, angered by Mark's death, manages to take out Five's blade and break free of Phiri's tentacles. When none of his offensive Legacies start working, John manages to use his Telepathy, and warns Sam, who is in the basement with Malcolm, a dozen scientists, and the five Chimærae. Phiri regains control over John, and goes down the elevator with Thin Mog and a couple dozen Vatborn. As they walk through the bunker, Thin Mog takes control of a group of marines, and uses them to kill more soldiers as they go. Suddenly, they are attacked by Ran, who blows up the marines and many of the Vatborn that are with them after Nigel, Bertrand, and Fleur disarm them. The four of them, all armed, stop when they see John, and he yells at them to run, but it's too late. Phiri Dun-Ra makes six icicles and kills Fleur with them before she can react. Bertrand attempts to save Fleur, but he is burned to death by Phiri, who engulfs him in a fireball. An enraged Nigel opens fire, but Phiri makes the gun he has backfire and knock him out, before Ran grabs Nigel by the waist and runs with him. Ran and an injured Nigel barely escape. As they follow them, John, Phiri, Thin Mog and the Vatborn run into Sam, and he uses his Technopathy to turn off the lights. Sam disappears, and lets Five out of his cell. Five starts to kill all the Vatborn surrounding them, and challenges Phiri to a duel.
Six, Marina, Nine, Ella, Lexa, and BK quickly fly the Loric Ship to Patience Creek, while Adam, Rex, and Dust stay with the Warship. Ella's power to detect life miles away (which she gained when she fell into the Loric Pit) starts to fade, and she doesn't know if anyone is alive at Patience Creek. Suddenly, Setrákus Ra contacts all Warships, including the one they hijacked, yells at Humanity for not listening to him, and commands all Warships to open fire on their cities. The Mogadorian invasion of earth begins again.
Five finishes killing all of the Vatborn around until only Thin Mog and Phiri remain. Five starts to fight Phiri, and John manages to break free of her tentacles that are pierced into his back after Five slices them off with his blade, which was thrown to him by John. Unfortunately, Thin Mog starts to take control over Five, but this ends when Sam reappears and blasts Thin Mog's head off. Phiri Dun-Ra keeps fighting Five, and almost subdues him. Suddenly, Shadow Mog appears and extracts Phiri, accidentally taking Five with them. Sam comes to John's aid, and they together kill Shadow Mog, who returned to finish them off. Walker, Lawson, Caleb and Christian arrive to help. The third Trueborn, Piken-Mog, suddenly arrives and catches Christian. Before the Piken-Mog can kill Christian, Christian is revealed to be nothing more than a duplicate of Caleb. Caleb apparently has a Legacy that allows him to create duplicates of himself. Caleb creates a diversion by creating more duplicates to fight the Piken-Mog. As they run away, they run into a dozen Vatborn that have been turned into stone by Daniela. Daniela then appears, and turns the Piken-Mog into stone as well. A weakened John, as well as Sam, Caleb, Daniela, Walker, and Lawson meet up with Nigel and Ran, who are holed up with Malcolm, a few remaining scientists, Agent Noto, and the five Chimærae, all of which survived. They also run into Five, who looks on as they all see 18 major cities being razed to the ground on monitors. Tens of millions of people are now dead.
Six, Marina, Nine, Lexa, BK and Ella reach Patience Creek and pick up the survivors (John, Five, Sam, Daniela, Nigel, Ran, Caleb, Walker, Noto, Malcolm, Lawson, the five Chimærae, and the few scientists). Lawson contacts all of the leaders of the world's countries, and they plan to do one simultaneous attack on the 20 remaining Warships with help from the armies of earth and many Human-Garde, which includes the President's daughter Melanie. After a run-through with Lawson, they drop him off at Pittsburgh with Walker, Noto, and the few scientists. Six and John persuade Nigel, Ran, Caleb, and Daniela to stay behind so they can live and lead the Human-Garde as the defenders of earth, also giving them the five Chimærae as protectors. Stanley goes to Sam, Biscuit goes to Daniela, Gamera goes to Ran, Regal goes to Caleb, and Bandit goes to Nigel. After Walker thanks John and Nine for giving her redemption, John requests Walker to look after the Human-Garde as a Cêpan. Then John, Five, Six, Marina, Nine, Ella, Lexa, Sam, Malcolm, BK and Stanley fly to Niagara Falls, where Adam, Rex, and Dust are waiting for them in the Warship. They split into groups and go around the world to the Loralite deposits, giving the governments of Earth the cloaking devices so they can take down the Warships. Sam and Six spend a few minutes to see the world while they do it.
Rex then pilots the Warship to West Virginia. Five teaches Malcolm how to handle the guns, while Adam teaches Sam how to power the Warship with his Technopathy. John makes a Voron dagger out of the noose that scarred him and Setrákus Ra. Nine reconciles and apologizes to John about everything he's done to him. Nine calls John his brother, and the two hug. John tells the team the plan. He, Five, Six, Marina, Nine, Adam, BK, and Dust will go fight Setrákus Ra, while Ella, Lexa, Sam, Malcolm and Rex pilot the Warship. John tells Adam that if things go south, he should return to the Warship and destroy the mountain base. John calls Lawson to send the order to attack the other Warships. All over the world, Humans and Human-Garde alike fight back against the Mogadorians.
Six creates the biggest storm she could ever conjure. She weakens the Anubis, but the Anubis also weakens their Warship. Five and Malcolm, with help from John, shoot down hundreds of Skimmers. Sam attempts to restore the shield's power, but ends up shutting off the entire Warship. As they fall, Six destroys the Anubis' main cannon with a dozen bolts of lightning. She summons three tornadoes and sucks away the Mogs in the ship. As they're about to crash, Six puts everything she has into the superstorm. Sam, with help from Rex, powers the ship back on, and the Anubis is destroyed.
John, Five, Six, Marina, Nine, Adam, BK, and Dust get ready to go down to fight Setrákus Ra. Lexa helps by pushing the other skimmers out of the hangar of their Warship, causing a diversion. Lexa flies them down, and they fight thousands of Mogs and dozens of Piken. Five flies Adam, Six, and Dust through the base so they can shut down the controls to the base, drops them off, and returns to battle to fight alongside John, Marina, Nine, and BK. Rex, Sam, Malcolm, and Ella bombard the rest of the Mogadorians with the Warship, and Marina creates an igloo to shield them. The group heads inside. As they get further into the base, they are attacked by an Augmented Trueborn that can fly, which John quickly kills. They see many dead Human-Garde, some of them from Russia, the rest from North America, who have been drained of their Legacies and killed. Then, Setrákus Ra himself comes out of the black ooze, and fights John. John is no match for him, and Setrákus Ra seemingly kills Number Five by drowning him in the black ooze.
Adam and Six, along with Dust, make it to the control room of the mountain base in order to shut down the controls. They make short work of the six Trueborns there and shut down the controls. Before they can go help the others, they are attacked by Phiri Dun-Ra, who was looking for them. Phiri impales Six with one of her tentacles, and Dust is quick to attack her. Phiri restrains and fatally wounds Dust before going back to attacking Adam and Six. Six subdues Phiri, but Phiri breaks free when Six is distracted by a Trueborn that Adam kills. Phiri grabs Adam with her tentacles, and Adam attaches himself to Phiri, creates a massive earthquake, and throws the two of them into a deep ravine created by his earthquake, killing Phiri and presumably Adam too. Six goes unconscious before she can save him.
John throws everything he can at Setrákus Ra to no avail. After attacking Setrákus Ra, BK is incapacitated by Setrákus Ra's black ooze. As John and Nine attempt to use strategy on Setrákus Ra, he reveals that he is more powerful than all Garde thanks to his Augmentations. He turns into Eight, and tries to seduce Marina. John freezes Setrákus Ra's legs to stone and Nine attacks him with the Voron dagger. Nine, thinking he's killed Setrákus Ra, loses his arm to Setrákus Ra's Augmentations when they wrap around his arm. John attempts to telepathically communicate with Adam and Six to no avail, but manages to contact Sam on the Warship. He requests Sam to blow up the mountain with the Warship. Suddenly, Marina manages to accidentally wound Setrákus Ra with her healing ability, which removes Augmentations. John takes the hint, and sends Marina and Nine off to save Six. John's healing Legacy keeps removing Setrákus Ra's Augmentations, slowly degrading him to the centuries old man he is. Setrákus Ra's ooze wraps around John and mortally wounds him. Setrákus Ra attempts to dig out John's heart. As Sam starts to bombard the mountain, John imagines Sarah one last time, and then hits Setrákus Ra with everything he has until nothing comes out.
Six regains consciousness, and notices that Dust had dove after Adam. Marina and a wounded Nine save Six. She tells Ella to destroy the mountain whenever she gets John out, whenever Setrákus Ra dies. After Marina and Nine leave, Six finds John, seemingly dead. She also finds Setrákus Ra, barely alive. She uses the Voron dagger to decapitate Setrákus Ra, and end the war. As BK suddenly breaks free of the ooze, John, who is alive but in a bad way, regains consciousness and starts to heal himself. Six kisses John, because they did it. She gets him and herself onto BK's back and tells Ella that they are on their way, just as the sun rises.
One year later, John and Ella are at the Himalayan Prophecy cave. John is in exile with BK and the Vishnu Nationalist Eight keeping him company, while Ella goes to a small school nearby. John had removed all the prophecy paintings, and he has made a table for the Elders of Earth. After saying goodbye to BK and Ella, John flies to a recently built Earth Garde Peacekeeper Academy near San Francisco, where Nine (still missing an arm) and Lexa are leading the Human-Garde as the defenders of Earth. John then visits Daniela, who had been helping people rebuild New York. Daniela had re-united with her mother. John also says hi to Karen Walker in Montreal and gives her a gift. Walker had been tracking down and killing the last of MogPro. John also visits Adam, who was dragged out of the ravine by Dust (the Chimæra died of his injuries). Adam is with the last of the Trueborn, including his sister Kelly as well as Rex, in an Alaskan prison camp. John asks Adam and Rex if they want to leave, but Adam says that it's better this way, as they are helping the Trueborn survive. After giving Adam a gift, John goes to visit Paradise, Ohio. He reminisces on Mark and Sarah, stopping by their old houses. John also visits Malcolm and Sam's mom in Paradise, and Malcolm asks John to tell Sam to come home and finish his education. John visits Sam and Six as well, who are traveling the world together. He gives them the same invitation gifts that he gave Ella, Nine, Lexa, Walker, Adam, and Malcolm. They are Loric Pendants that reveal the Loric symbol of unity. Marina, living in exile, is the hardest to find, as she never got over what happened in the war, and felt sorry about all those who died (Eight, Sarah, Mark, Adelina, Crayton, the Human-Garde, and the tens of millions killed in the invasion), especially after learning that Five is alive. Apparently Five survived the drowning, and John and Marina find him on a secluded island. Five appears to be near death, and John and Marina decidedly leave without giving him the pendant. When Marina goes to the Himalayas with John, she finally cries when she sees what he has done. She thanks John and kisses him. John and Marina prepare for the first meeting of the Elders of Earth. The last line of the series is "I'm done with numbers."