The Ghost Backstage (Haunted Library Series #3)

Kaz and Claire’s new detective agency is a success! Their latest case, though, is proving to be the hardest yet. When Claire’s classmate says he saw a ghost backstage while rehearsing the school play, Kaz goes to school with Claire to investigate. From the description the boy gave, Kaz is sure it’s his mom—but where has she gone? Kaz and Claire search everywhere and find no trace of her, but the mysterious ghostly activities are still happening…