about the matter. He tells her he believes that the bees are being used as a carrier for some sort of experiment. Skinner returns home where he is confronted by Mulder, who now suspects that Skinner has been working against him all this time. Skinner is able to convince Mulder that he would not have forced his own drawer lock open and hence could not have been the murderer. Convinced of Skinner's evidence, Mulder turns in the gun with the serial number filed off so Skinner is not blamed for the murder. That night Skinner confronts The Smoking Man in his apartment, angry that nothing has been done for Scully. The Smoking Man convinces him that Scully will die if he kills him and Skinner leaves without killing him, but not before firing warning shots. Shortly afterwards Covarrubias calls The Smoking Man, who tells her to tell Mulder what he wants to hear while an unknown man is shown behind her listening on another phone. Production Co-writer Frank Spotnitz described the episode as a "fortunate accident". Late in the fourth season of the show Gillian Anderson left the show for a week to film her part in the film The Mighty. The producers, knowing that they would have to write an episode without Dana Scully, decided it was not fair to have David Duchovny carry the same workload as in a normal episode considering her absence. As such, a story was devised in which his involvement would be light. This resulted in the decision to write, for the second year in a row, an episode focused on Assistant Director Walter Skinner (Mitch Pileggi). Howard Gordon, having written the previous Skinner-centric episode, "Avatar", joined Spotnitz and the two wrote the episode over a weekend while another Gordon-written episode, "Synchrony", was in production. The writers felt that this was the perfect time to bring in Skinner's deal with The Smoking Man (William B. Davis) to cure Scully's cancer, made in the episode "Memento Mori". Frank Spotnitz said of Skinner's deal, "The hard thing for Skinner was that we had to keep him in the middle. We had him tell Mulder not to bargain with The Smoking Man in order to save Scully's life. And then he himself struck a Faustian bargain with the Cigarette Smoking Man and was in his debt for some kind." The writing staff felt that "Zero Sum" was