Mr Satterthwaite is in Corsica with the Duchess of Leith, a somewhat difficult, autocratic and miserly lady. After a difficult crossing from Cannes, they settle into the hotel and at their first meal there the duchess spots a young lady she knows called Naomi Carlton Smith. She is a distant relation of the duchess and is a bohemian artist who was involved with a young writer who the year before was accused of stealing jewellery and imprisoned. The duchess enquires if she has a car and finding out that she does, insists on her driving herself and Satterthwaite on a tour of the island the next day. However as it is only a two-seater the duchess inveigles another guest at the hotel called Mr Tomlinson into joining them with his four-seater car. At the appointed time they drive up into the mountains and eventually stop where the road finishes at an isolated coastal village of the name of Coti-Chiavari which Naomi terms "the World's End". There, Satterthwaite is delighted to see Mr Quin sitting on a boulder looking out to the sea. He has a feeling that Quin has turned up "in the nick of time" but he cannot fathom why he feels that way. The group has brought a picnic with them but as it is starting to snow they shelter in a cassecroute wherein they find three other visitors from England: a theatrical producer called Vyse, a famous actress called Rosina Nunn and her husband, Mr Judd. They are also enjoying a picnic and the two parties settle down to eat.
During the conversation that ensues, Miss Nunn admits to her constant habit of being absentminded and the occasion she almost lost her pearls, which were insured, unlike her stolen opal. The thief was called Alec Gerard, a young playwright, who supposedly took it from her theatre dressing room. Although the jewel was not found on him, he was unable to satisfactorily account for a large sum of money that he was able to pay into his bank the next day. Miss Nunn has cause to empty her bag and within it is wooden box which Mr Tomlinson recognises as an Indian Box. Realising that no one knows the true nature of such an item, Tomlinson shows the group how the box contains a secret compartment and they are all shocked when the missing opal is found within it. They realise the miscarriage of justice that has occurred. Satterthwaite and Quin again bid each other goodbye at the remote spot.