Each found guilty of an irredeemable crime, four robots find themselves banished from their home world and bound together by the Kill Lock--a programming link that means if one of them dies, they all will. Now a soldier, an addict, a murderer, and a child find themselves forced to protect each other while in search of a cure to survive. Their only clue is a bot known as The Axial, supposed to be the creator of the Lock and keeper of its secrets.