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.

Mulder and Scully travel to Gibsonton, Florida, a town built and populated by circus and sideshow performers to investigate the death of Jerald Glazebrook, The Alligator Man. While searching for leads on the killer, the agents come across many bizarre characters including the local sheriff who was once known as Jim Jim, the Dog-Faced Boy.