There's been a spate of break-ins lately in the area and everyone in Kate's class is saying that the burglar is Desmond Locke's dad because he's just come out of prison. Everyone, that is, except Kate. She's sure that Mr Locke is innocent and turns to her Secret Seven books for inspiration - they always find the real thief. Kate and Desmond become detectives to find out the truth and prove Desmond's dad is innocent. But the truth isn't always what you would like it to be and Kate is horrified when she discovers who really is... GUILTY.