Poirot has always hated visiting the dentist, but this time his check-up is painless and soon over. As he leaves Mr Morley's surgery, he observes a woman wearing patent leather shoes with large buckles. She catches one of the buckles on the taxi door and wrenches it off, and as Poirot hands it back, he is reminded of the children's rhyme 'One, two, buckle my shoe'. Back home, Poirot is astonished to receive a call from Chief Inspector Japp, informing him that Mr Morley has shot himself. There was no reason for him to commit suicide, and Poirot believes he was murdered, but who would want to kill an inoffensive dentist? To find out, Poirot must pick up sticks and lay them straight... As Poirot starts to dig and delve, the solution seems apparent. But with so many suspects, and a wealth of motives to digest, he has a long way to go before his plate's empty...