Thirty years after excavating the ancient birdman tablet from the Cahokia Mounds, Dr. Melvin Witty, a brilliant archaeologist, is visited by the ghost of the tribe’s leader with a warning to return the tablet or prepare for sacrifice.

After stealing the tablet from the Cahokia Museum, and handing it off to a group of unwitting high school students, Melvin, the students, and their teacher are sucked into the underworld of Cahokia.

They have until sunrise to return the tablet – or they’ll be stuck there forever.