S7E18 · Brand X

In Winston-Salem, North Carolina, Walter Skinner (Mitch Pileggi) is charged with guarding the life of Dr. James Scobie, a former researcher who is testifying against his former employer, the Morley tobacco corporation. Prior to his trial, Scobie develops a cough, but shrugs it off. In the morning, Skinner and Scobie's wife find his body on the bathroom floor, with his face ripped away.

Morley has created a form of "super-tobacco", which is inhabited by a genetically engineered tobacco beetle whose eggs can survive the process of cigarette manufacturing and are released in the smoke of the cigarettes. The cigarettes were tested on a range of subjects by Scobie and his colleague, Dr. Peter Voss. Of the four human test subjects, chain smoker Darryl Weaver is the only surviving participant. Prior to his death, Scobie agreed to give Weaver an unlimited supply of cigarettes in exchange for his silence; he subsequently pressures Voss into honoring his "arrangement" with Scobie.

A chain of victims soon succumb to the eggs contained in the toxic smoke, all of whom are found with their bodies covered in the tobacco beetles. While interviewing Weaver, Fox Mulder (David Duchovny) is exposed to the smoke, later coughing up blood and needing his lungs invasively cleared as the beetles begin to hatch.

Voss, who had until now been hiding behind his legal advisor, has a change of heart upon hearing of Mulder's condition and tells Skinner of the aforementioned testing. Skinner goes to Weaver's apartment after getting his name from Voss and finds Morley's director of security bound and gagged. When Skinner removes the gag, the man chokes and beetles begin crawling from his mouth. At the hospital, Mulder is in grave danger due to the eggs now hatching in his lungs, and Dana Scully (Gillian Anderson) attempts to find a way to save him, because he is now "too weak for thoracic surgery."

Meanwhile, Weaver attempts to browbeat Skinner, threatening to light one of the toxic cigarettes. As Weaver attempts to leave the building, Skinner shoots his shoulder and the pane of glass behind him, leaving him injured and covered in glass. He drops his cigarette to the floor and Skinner snuffs it out with his shoe. Back at the hospital, Scully realizes that nicotine might save Mulder's life. She is correct in her solution, noting that the high level of nicotine in Weaver's system didn't allow the beetles to develop. Scully administers nicotine to Mulder, who in turn recovers, albeit with a sore throat, as well as a minor addiction to nicotine, which drives him to buy a pack of Morley cigarettes for himself. Chided by Scully, he throws them out, but then stares at them pensively after she leaves.