I don't know. But Arthur's totally lost his mind, people are forgetting stuff and records aren't matching up with what people are remembering. Buffy thought it could be Barron, but I'm not convinced, Martha suggested Nanomites someone stole from Rex, but I doubt it's that either.

... Howie thinks we're all just going crazy because this place is stressful, but I'm sorry, I've been through a lot in my life, and I've never just invented new memories to help me cope with something.