S2E22 · F. Emasculata

In the Costa Rican rainforest, entomologist Robert Torrance discovers a decomposing boar carcass covered with purple pustules. While examining one, it bursts, spraying him with fluid. By nightfall, Torrance develops similar boils and attempts to radio for help. When soldiers arrive the next morning, Torrance is dead.

Simultaneously, in Dinwiddie County, Virginia, a prison inmate also named Robert Torrance receives a package containing an infected leg of meat. A pustule on the meat erupts, and Torrance dies within thirty-six hours. Two other inmates, Paul and Steve, clean Torrance's cell but escape in a laundry cart. Fox Mulder (David Duchovny) and Dana Scully (Gillian Anderson) are sent to help the U.S. Marshals find them. The agents are surprised when the prison is quarantined by the CDC and the National Guard: Mulder decides to join the Marshals to hunt the fugitives while Scully investigates the prison.

Scully discovers that the prison population is infected with a lethal contagion. She finds a pile of body bags ready for incineration and examines Torrance's corpse. Dr. Osbourne from the CDC tries to stop her, but a pustule on Torrance's body erupts in his face. Scully traces Torrance's package to Pinck Pharmaceuticals, a major drug developer, and finds an insect in another prisoner's body. Dr. Osbourne, now visibly infected, reveals that his team works for Pinck and is researching a dilating enzyme produced by the insect. The insect has a parasitic life cycle that kills its hosts. Osbourne claims that Pinck deliberately introduced the insect and contagion into the prison as an experiment. He soon dies, and his body is burned.

Meanwhile, the fugitives murder a man, steal his campervan, and stop at a gas station. Paul calls his girlfriend, Elizabeth, for shelter. They knock out the gas station clerk and escape in his car, evading the Marshals. Mulder witnesses a CDC biohazard team taking the clerk away. Scully warns Mulder that the contagion could spread if the fugitives are not captured. The fugitives reach Elizabeth's house, where she tends to Steve, who is in the late stages of infection. As Steve dies, a pustule erupts in Elizabeth's face, infecting her.

Mulder and the Marshals raid the house, and while they manage to arrest Elizabeth, Paul escapes. Mulder therefore decides to confront Skinner and The Smoking Man, suspecting he and Scully were deceived into taking the case. Mulder argues that the public should know the truth of the situation, but the Smoking Man argues it would cause mass panic, which Scully agrees with.

Questioning Elizabeth, Mulder learns Paul plans to flee to Toronto by bus. Mulder and the Marshals track down the bus and surround it. Mulder persuades a panicking Paul to release a teenage hostage, but before Paul can divulge any information, he is shot dead by the Marshals. Later, Scully explains that Pinck sent the package to a namesake of the dead entomologist to disguise their wrongdoing as a postal error. Mulder confronts Skinner in his office, determined to go public. Skinner, however, warns him they lack evidence, and he tells Mulder to be more cautious in future cases.