...okay, now I want to see if there's a way to bring in the actual Crystal Skull, or just one more of Quetzalcotl's skull devices, and still have it fit the prompt. Paul Davis could make a surprise guest appearance! I don't know, maybe some guy has fled New York under some kind of serious Adler-level allegations, and the White Collar team has to investigate his mansion, which is full of weird artifacts. Then Neal stares into the eyes of the skull too long and disappears, but the skull is slightly defective and doesn't shift him out all the way, leaving him with some limited ability to interact with the world around him; after the reports get filed, Davis (who must be a Colonel or something by now, seriously) shows up and wants them to hand over the crime scene to a governmental organization Peter's never heard of before, citing national security. But Davis being Davis, Peter is able to convince him to give the White Collar team 24 hours to see what happened to Neal. So the team ends up working through the night in this guy's mansion, with Neal trying desperately to communicate with them and most of them just thinking the place is haunted.

Also, Peter and Diana, yes. I would not be disappointed if every fic I wrote for this involved Diana, because Diana. ...I feel like the two of them fighting their way out of somewhere would be amazing, because everyone would underestimate them ("Hey, it's some old guy and a chick!"), and then they would regret that. Like, a lot.