The X-Files

Zero-Sum (4x21)

Air date: Apr 27, 1997

Skinner destroys evidence to cover up a woman's death and poses as Agent Mulder to complete the task. Mulder finds out about Skinner's deception and confronts him, and Skinner reveals that he is working for the Cigarette-Smoking Man in order to obtain a possible cure for Scully's cancer.