The Island is the site of the Plum Island Animal Disease Center (PIADC) which was established by the United States Department of Agriculture (USDA) in 1954.
Plum Island is owned in its entirety by the United States Government. Access to the island is controlled by the United States Department of Homeland Security (DHS) which restricts access to orindary citizens. The Facility is occupied by Mogadorians and is the location of their Chimæra experimentation. The main annex is mostly staffed by Marines and human scientists while a separate warehouse-like building, off to one side, is staffed exclusively of Mogadorians.
Adam first learns of the Island from Rex, the lone Mogadorian survivor of the destruction of the Dulce base, who reluctantly tells him about the Chimæra in captivity there. Adam decides to travel there and rescue them, with the help of Rex and Dust, a Chimæra who had been held in Dulce.
When they approach the Island, Rex ties Adam up and pretends that he is his prisoner in order to get into the base. Adam is locked in a cell while his father is called. Rex manages to free Adam a few days later and leads him to the Chimæra.
The first two Chimæra have been badly tortured to the point of mutilation and insanity and they are forced to leave them behind. They find five other Chimærae and set them free, they try and escape but the alarms are sounded. Rex leaves Adam, telling him that he has fulfilled his promise to help him and that he understands that he has his reasons for what he is doing but cannot go any further as he belongs with the Mogadorians.
At the command centre on the top floor another alarm is sounded stating that the location of the Garde has been found in Chicago. Hours later Adam is driving to meet them while frantically trying to reach Malcolm on his Cell Phone.
The Plum Island Mogadorian facility is located within the US government's Animal Disease Centre and is thought to be dedicated to the research and experimentation of animals. To date it is known for experimentation of Loric Chimæra in order to identify and replicate the gene which makes their shapeshifting capabilities possible.