"I'm not sure," he admits. The mall's a pretty desolate thing, as they're walking through it, and it occurs to him that he doesn't remember the last time he set foot in one of these. Several storefronts on the way to JC Penney are empty; while there are a few old women getting their steps in, the actual shoppers are spread thin. "I've been racking my brain, but I don't see how much we can pick up without access to witnesses or tangible evidence. You showed up, Scully disappeared, and as far as either of us know, it's a totally unique case. I don't have any other examples of alleged time travel that work like this. We're at a standstill."

Except.

Mulder doesn't like suggesting it, but it's the only idea left in his arsenal. "Unless we look up your house and see if you left a key under the mat, of course."