When a man is killed and his liver is eaten but the security cameras didn't pick up a thing and the only entrance to the room is a narrow air vent, Mulder and Scully wonder just how he did get in to commit this crime.

Scully is brought onto this case by FBI agent and classmate, Tom Colton who doesn't suspect anything out of the ordinary and won't take anyone suggesting otherwise. Mulder persuades Scully to let him on this case and she eventually agrees.

When another man is killed in the same fashion and with no possible entrances it seems that Mulder's theories of a genetic mutant who can elongate himself to climb through the smallest possible route might seem slightly plausible. Especially when elongated fingerprints found at the crime scene match a man called Eugene Victor Tooms who, according to records is 100 years old.

While investigating his apartment, the two agents come across a nest of newspaper and bile. Mulder comes to the theory that Tooms needs to kill 5 people and collect their livers so he can go into a hibernation state for another 30 years. All he needs is one more victim and he targets Scully.

While in her apartment, she is attacked by Tooms but Mulder luckily comes to her rescue (for the first of many times) before he can kill her. They have finally caught him. It is Mulder's words at the end that really do sum up all our fears:-

'All these people putting bars on their windows. Trying to feel safe. I look at this guy and I think, it's not enough'