When moonlighting medical students harvesting skin from a corpse for temporary use accidentally take it from the wrong donor, the results are catastrophic: a New York City hospital ward is destroyed in a bloodbath, and an elderly professor, admitted for a routine skin graft, is suddenly the city's most wanted fugitive.

Agents Fox Mulder and Dana Scully are the only ones to suspect something more ominous than a medical procedure gone awry. As the FBI agents investigating the "X-Files"—strange and inexplicable cases the bureau wants to keep hidden—Mulder and Scully are determined to track down the forces they suspect are behind the murders.

While the police hunt the fleeing professor, Mulder and Scully track the skin that was grafted onto him, a trail that leads from the morgue to the headquarters of a cutting-edge biotech company to the jungles of Thailand. Together they begin to uncover an unholy and undeniable alliance between a battle-trained plastic surgeon, international politicians, and a legendary Thai monster known as the Skin Eater.