Thirteen-year-old Grace is grieving over her father's mysterious death, dealing with her distraught mother's erratic parenting, and evading her creepy nosy neighbour, Mr. Stuckless. She and her friends like to get away from it all by hunting for fossils near their secret hideaway in an abandoned mine. But when Grace receives a strange note about her father's death, it sets off a chain of events that leads to Grace and her friends trying to solve the mystery behind her father's disappearance. As clues and suspects start piling up and the investigation becomes more dangerous, Grace and her friends find themselves racing against time through abandoned mine shafts to figure out what really happened to her dad.