The title of the finale refers to Yves Adele Harlow, the beautiful, enigmatic computer hacker on "The Lone Gunmen," played by British actress Zuleikha Robinson. Revelations about her background are planned as part of the arc of "Gunmen's" second season.

"That's exactly right," says Spotnitz. "It's the beginnings of the mythology of that show."

Duchovny also makes a guest appearance in that episode, as Mulder has an inadvertent rendezvous with the Gunmen's partner, Jimmy Bond (Stephen Snedden).

Sharp-eared fans of both series may have been puzzled when, in an episode airing April 6, the Gunmen referred to calling their old friend Fox Mulder. At that time, over on "The X-Files," Mulder was still believed dead, his apparently lifeless body having been returned (in an April 1 episode) by the aliens that abducted him last season. He was not discovered to actually be alive until the "X" episode that aired April 8.

In other words ... oops.

"Yes, yes, yes," says Spotnitz. "You have to forgive the timeline inconsistency, because we had no idea, when we wrote that script and shot that episode, when it would land on the air."

"So you just have to assume that it took place not on the Friday before 'The X-Files' in which he came back to life."