Luke, a friend of the Five Find-Outers, is working in Lady Candling's garden when her valuable Siamese cat is stolen.

Next door to Pip and Bets Hilton lives Lady Candling, whose prize cat, Dark Queen (a valuable Siamese), disappears under the nose of Luke, the gardener's help and a friend of the Find-Outers.

Mr Tupping, (the gardener), is a nasty character who the children immediately decide could be the thief, but he wasn't in the area when Dark Queen was stolen.

Mr Tupping is still the prime suspect though and it turns out that he stole Dark Queen in the morning, then painted a small patch of cream-colored paint to another cat's tail to disguise it as Dark Queen, who had a distinctive cream patch on its tail.

In the afternoon, Mr Tupping rubbed the paint off the bogus cat's tail and then announced Dark Queen was gone.