The Keepsake (Rizzoli & Isles #7) by Tess Gerritsen

For untold years, the perfectly preserved mummy had lain forgotten in the dusty basement of Boston’s Crispin Museum. Now its sudden rediscovery by museum staff is both a major coup and an attention-grabbing mystery. Dubbed “Madam X,” the mummy–to all appearances, an ancient Egyptian artifact– seems a ghoulish godsend for the financially struggling institution.

But medical examiner Maura Isles soon discovers a macabre message hidden within the corpse–horrifying proof that this “centuries-old” relic is instead a modern-day murder victim.