You Have to Stop This: The Secret Series, Book 5 (paperback) Pseudonymous Bosch
I always feared this day would come. A secret is meant to stay secret, after all. And now we've come to this: the fifth and final (I swear!) book in my saga of secrets.
A class trip to the local natural history museum turns dangerous, or perhaps deadly--and I don't mean in the bored-to-death way--when Cass accidentally breaks a finger off a priceless mummy. Forced to atone for this ""crime"" of vandalism, Cass and her friends Max-Ernest and Yo-Yoji go to work for the mummy exhibit's curator, only to be blamed when tragedy strikes. To clear their names--and, they hope, to discover the Secret--the trio must travel deep into a land of majestic pyramids, dusty tombs, mysterious hieroglyphs, and the walking dead. Egypt? Or somewhere much stranger . . .
In the midst of it all, the Secret still lurks. You're out there, reading and talking about it, and now my life--and chocolate supply--is in the greatest danger yet. So please, with a cherry on top, I'm begging you: you have to stop this!"