Adopted by the owner after being mysteriously abandoned as a baby on the steps of his infamous establishment, Cat has grown up backstage. When Cat overhears a conversation about a diamond hidden somewhere in the theatre, she's determined to find the treasure.
Ably assisted by Pedro, a musician in the company orchestra, she is thrust into a world of drama and intrigue, where she encounters Covent Garden street gangs, boxing matches, theatre riots and spectacular stage productions. En route, she learns a lot about who she is, and who her real friends are...