In Aunt Tilley's house, Kyla and E.B. investigate random objects in the file drawers they inherited from Great Aunt Hermione that show how history connects to who we are and how we live now. Today's mystery is "Cause of Death". Kyla visits an archaeological museum, examines a mummy, and learns that teeth are important clues for archaeology. Dental infections caused the death of some people preserved as mummies, and bits of rock included in their ground flour helped wear down their teeth. E.B. takes a mummy replica tooth to a dental school, where he learns more about teeth and ancient dental care.