Max is a pampered cat, used to the finer things in life, until a fun mouse chase goes badly wrong and he finds himself scruffy and alone and hiding out at the Theatre Royal. It's here that Max takes on his first case as a detective cat, when he notices that famous singer Madame Emerald is acting strangely. Why is her maid so terrified? And what kind of singer doesn't like to sing in public? Soon Max is trapped in complicated web of crime, dashing round dancers' legs and over the rooftops of London in a race to catch a clever thief.