Investigating the theft of a Sintillian heart, Kay learns the culprit is Alpha, his former mentor and the man who left him for dead years ago. But Jay and Kay discover Alpha now has multiple body parts grafted onto his body, becoming even more dangerous.

When Kay is infected with Millicrons, Jay takes his place on an assignment to transport a symbiote named Troy to New York City. He has to do it within twenty hours or be permanently absorbed by Troy. But Buzzard returns and is looking to capture the symbiote for his mysterious boss.

Alpha is back and his alien attachments are falling apart. At first, he forces Jeebs to locate new alien body parts for him. But when Alpha discovers Troy the symbiote is at MIB, his plans change.