Mr Satterthwaite had forgone his usual trip to the French Riviera and is instead on holiday on a Spanish island. Regretting the fact that there is no one there that he knows or who is of a sufficiently high social standing, he occupies his time by walking and often goes to the garden of a villa called La Paz which stands on a high cliff overlooking the sea. He has developed a love of the garden but the villa, which is shuttered and seems empty, intrigues him. He imagines it to be the home of a once-beautiful Spanish dancer who now hides herself away from the world
After exchanging pleasantries with the gardener, Satterthwaite makes his way to the cliff edge and soon hears approaching footsteps. It proves to be a somewhat boyish-looking man who is nevertheless over forty years of age. The man seems annoyed that he doesn't have the spot to himself and tells Satterthwaite that he came here the previous night and found someone there seemingly in fancy dress in, "a kind of Harlequin rig". Satterthwaite is surprised at this mention of his old friend and tells his new acquaintance that Mr Quin's appearances usually presage revelations and discoveries. The younger man comments that his appearance seemed very sudden, as if he came from the sea.
The man introduces himself as Anthony Cosden and tells Satterthwaite of his ordinary life to date however he has now been told by a Harley Street doctor that he has cancer and only six months to live. He came back to this island which he had visited some twenty years before and the implication is given that before he fell too ill he meant to kill himself by throwing himself from the cliff. He has been thwarted in this intent now on two occasions: the previous night by the man in the Harlequin costume and now by Satterthwaite. The elder man seeing providence interfering tries to persuade Cosden not to take this path but the younger man is good-naturedly resolute saying that he will return when neither Satterthwaite nor anyone else is there and carry out his intention.
Cosden leaves and some impulse takes Satterthwaite up to the villa. Pulling open one of the closed shutters, he sees a troubled woman in traditional Spanish dress looking at him. He stammers an apology which makes the woman realise that he is English and she calls him back when he turns to leave. She too is English and she invites him in the house for tea as she wishes to talk to someone. She unburdens herself on Satterthwaite telling him that she has lived here for most of the last twenty-three years, all but the first year of that being a widow.
She married an Englishman when she was eighteen and he bought the villa for them. The marriage proved to be a dreadful mistake as her husband abused her to the point where her baby was stillborn. Some girls staying in the local hotel dared him to try and swim off the dangerous sea at the base of the cliff and he foolishly accepted. He drowned and his body was battered against the rocks as his wife watched. Soon afterwards, suffering loneliness, she had a brief affair with a young Englishman who was visiting the island, the result of which was an illegitimate son born nine months later. He is now grown up and happy, not knowing of his father and serious with a girl whose parents want to know his antecedents should they want to be engaged. To save him pain and scandal, she is planning to commit suicide to hide the truth from him forever. For the second time that day, Satterthwaite find himself persuading someone not to take their life. He asks her to take no action for twenty-four hours but to leave the shutter he opened unlatched and to wait there tonight. He returns to the hotel and finds Cosden and refers obliquely to the shutter on the villa that he opened. Cosden understands his meaning and leaves.
The next day he goes back to La Paz and finds the Englishwoman there, her entire appearance transformed with happiness. She and Cosden, reunited after twenty years are to be married by the console that day and she will be able to introduce her son to his father. She refuses to accept that Anthony will die. She will make sure he lives.
Satterthwaite makes his way back to the cliff top and is not surprised to find Quin there. His friend smilingly pretends not to know what Satterthwaite has been up to but tells him that the man who drowned in the sea twenty years ago truly loved his wife – almost to the point of madness, and the desire to make amends for past transgressions can sometimes be so strong that sometimes a messenger can be found. As Satterthwaite leaves, Quin walks back towards the cliff edge, destination unknown.