When Lily learns that a strange monster might be living in the school’s bathroom, she knows that the Cryptid Club have found their next case! But when the Club discovers strange writing on the bathroom stalls and that something is stealing paper and pens, they know it’s going to take some super-duper sleuthing to crack this caper. But when the monster starts popping up in every toilet around the school, things quickly go from bad to the worst! The principal has orded all the bathrooms closed - immediately! Now Lily, Henry, Oliver, and their new friend Ernie have to solve the mystery before the entire school has an accident of epic proportions.