Jeff's older sister Kim takes pleasure in teasing and scaring him. When their father — a museum curator — has a mummy case accidentally delivered to their house, Kim is up to her old tricks. After the case is put in the basement for safekeeping, Kim dares Jeff to enter the basement and touch it. Jeff is reluctant, but he eventually agrees. As soon as he steps in, Kim locks him inside. To his shock, the chains on the mummy's container begin to rattle and the lid moves. Jeff screams and darts up the stairs. He tells his sister what he saw, but the lid doesn't seem to have moved at all.
Later that night, Jeff has trouble sleeping. He hears what sounds like footsteps and fears the mummy has come to life. When night falls the next day, Jeff waits for the mummy to awaken. Eventually, it stumbles into the kitchen and reaches out for him. The noise wakes up Jeff's parents, and the mummy flees back into the basement. Jeff's father reveals there was a rumor that suggested — if the locks on its case were ever removed — the mummy would come to life.
Jeff goes to bed, but Kim sneaks into the basement, intending to remove the chains and scare her brother. She's shocked to find the lid has been removed. The door locks behind her, and Kim hears the mummy approaching.
- Jeff and Kim's father is mentioned by name in the book: Larry.
- This story has an abrupt perspective change from Jeff to Kim near the ending.
- The line, "Would you believe that the only books they had on mummies were scary novels and art history books?" could be a meta reference to the Goosebumps franchise, which contains several scary books about mummies, notably The Curse of the Mummy's Tomb and Return of the Mummy.
- The title is likely a parody of the board game Don't Wake Daddy.