For the first time ever, Rico has a friend coming for a sleepover. After weeks of not seeing each other, Rico and Oskar are reunited and start their adventure with the weekly bingo at the retirement home. But although Tanja wins two handbags, Oskar seems suspiciously grumpy and Tanja oddly sad. Oskar's dad leaves a bag in front of the door because he needs some distance from his son. So much heart affliction is too much for Rico. When Oskar finally tells Rico that Tanja was cheating at bingo the other night and that those ugly handbags she wins all the time are really expensive leather bags, Rico refuses to accept that his mother might be a crook; Ellie Wandback, the bingo host, must be blackmailing her. Since the Bühl is too occupied with a champagne-drinking redhead, Rico and Oskar seek help from sprightly pensioner Mr. van Scherten; together they try to find out what is going on. Not everything goes as planned, but in the end, the two young detectives discover more than just the truth about the bingo-cheat and the handbags.