Lady Candling lives next door to Pip and Bets, and owns some very expensive, pedigree Siamese cats. When her most famous cat, Dark Queen, goes missing, the gardener's help, Luke seems the obvious suspect. Mr Goon and Mr Tupping, Lady Candling's gardener are sure he's the culprit, as he was digging by the cat house all alone when Dark Queen disappeared. The Five Find-Outers must solve the mystery to clear the name of their friend Luke. Strangely, Dark Queen soon reappears, dirty and tired, but unhurt. And stranger still, she disappears again a few days later, once more when only Luke could have done it. Piecing together clues of pale paint, turps and some wellington boots, the Five Find-Outers prove, once more with the help of Inspector Jenks, not only that Luke is innocent, but that Mr Tupping took Dark Queen and deliberately tried to frame Luke for the crime.