After the obituaries of three identical men are e-mailed to Mulder, the agents are contacted by a CIA agent who tells them about a Russian Spy Killer sent to eliminate evidence of Cold War era Russian clones who had infiltrated the American medical establishment.

Invisible animals are rampaging through town, destroying property and trampling a federal employee. On arriving in town, the agents begin their search at a nearby zoo with the distinction of never being the site of live birth. Whether that's because as Mulder suspects, Aliens are 'harvesting'' the young or, as Scully insists, an animal rights group determination to close down the zoo, the only reliable witness appears to be a hand-signing gorilla named Sophie.