This novel by Agatha Christie features Belgian detective Hercule Poirot investigating a murder at an English country house called The Hollow, where tangled romantic loyalties and family secrets complicate the case.
Lady Lucy Angkatell, the charming and eccentric wife of Sir Henry Angkatell, prepares to host a volatile weekend at The Hollow, their country house. Her guests include Dr. John Christow, a brilliant Harley Street physician, and his wife Gerda, whom Lucy considers sweet but slow; Henrietta Savernake, a talented sculptor and Lucy's cousin, who is secretly John's mistress; Edward Angkatell, a gentle man who has proposed to Henrietta three times without success; Midge Hardcastle, another of Lucy's young cousins; and David Angkatell, an awkward young intellectual. Lucy also mentions inviting a detective she met in Baghdad to Sunday lunch.
In London, Henrietta is consumed by a clay sculpture she calls Nausicaa. After dismissing her model, she discovers that the woman's spiteful personality has seeped into the clay through her fingers and destroys the entire work, knowing the vision will not return. Meanwhile, John sits exhausted in his consulting room. His real passion lies at St. Christopher's Hospital, where he develops an experimental treatment for Ridgeway's Disease. His prize patient, Mrs. Crabtree, an indomitable elderly woman, shares his determination to fight. A phrase haunts him: "I want to go home." It conjures memories of San Miguel, where 15 years earlier he was engaged to Veronica Cray, a beautiful actress. He broke the engagement when she demanded he abandon medicine for Hollywood, then married Gerda, choosing safety over passion.
Gerda dreads the weekend, hiding behind a defensive strategy cultivated since childhood: appearing slower than she is so others underestimate her. At The Hollow on Saturday, Henrietta and Edward walk together, reminiscing about Ainswick, the beloved Angkatell family estate where Edward lives. He proposes again; she refuses, unable to imagine life without John. When the Christows arrive, John's commanding vitality makes Edward seem pale by comparison. Sir Henry brings out revolvers for target practice. Lucy shoots with startling precision; Sir Henry recalls she once saved his life by shooting two attackers on the Bosphorus.
That evening, Veronica Cray makes a dramatic entrance through the French windows. A dazzling film actress who has rented a nearby cottage called Dovecotes, she claims to need matches, recognizes John, and sweeps him away. At the swimming pool pavilion, she invokes their shared past, and John, overwhelmed, stays until the early hours. He returns realizing the encounter has freed him: Veronica means nothing, and it was only his unresolved guilt at having fled her that kept the memory alive. The next morning, Veronica demands he visit Dovecotes and insists they resume their relationship. John refuses firmly. She responds with fury. He walks back and sits by the pool, feeling liberated. He senses danger, hears a faint click, and turns, but a shot rings out before he can react. He falls by the pool's edge, blood dripping into the water.
Hercule Poirot, the fastidious Belgian detective, arrives for his luncheon engagement and is led to the swimming pool. He sees what appears to be a staged tableau: John's body by the pool, Gerda standing over him holding a revolver, and three others arriving simultaneously by different paths. The scene is real. The dying man opens his eyes, says "Henrietta" in an urgent voice, and dies. Henrietta steps forward, takes the revolver from Gerda's hand, and drops it into the pool with apparent clumsiness. Poirot notes this with sharp suspicion.
Inspector Grange takes charge, initially confident Gerda shot her husband. A forensic revelation upends the case: The revolver Gerda held is not the murder weapon. A .38 Smith and Wesson missing from Sir Henry's collection fired the fatal shot. The scene was staged, but Poirot cannot yet determine by whom.
The investigation spirals into confusion. Lady Angkatell admits she placed a Mauser pistol in her egg basket that morning but claims she cannot remember why. In private, she confesses to Sir Henry that she contemplated arranging John's death to clear the way for Henrietta to marry Edward and continue the Angkatell line at Ainswick, but abandoned the plan. Veronica tells Poirot a carefully inverted story in which John was pursuing her; Poirot sees through it. Henrietta visits Poirot and passionately describes John's devotion to medical research as the real center of his life. Poirot confronts her about dropping the revolver in the pool and about Ygdrasil, a distinctive tree design she habitually doodles, which he finds on a table in the pavilion at a time she claims she was not there. She denies killing John.
Edward proposes to Midge at a London restaurant after witnessing her degrading working conditions at the dress shop. She accepts but later breaks off the engagement, unable to marry a man who still loves Henrietta. That night, Midge hears Edward leave his room and finds him attempting to end his life in the kitchen by inhaling gas. She drags him out and revives him. Edward confesses he feels like a failure. Midge realizes what he truly needs is warmth and daily love. Edward sees her clearly for the first time, and they reconcile.
The missing revolver is found planted in Poirot's hedge, bearing fingerprints that match no one connected to the case. The inquest returns a verdict of murder by person or persons unknown. Lady Angkatell offers Poirot the truth if he lets the matter drop. He refuses.
Lucy warns Henrietta that the leather holster for the murder weapon has not been found and could be traced. Henrietta drives to Bexhill, where Gerda is staying with her sister Elsie Patterson. Gerda reveals the truth: On Saturday night, she followed John to the pool and saw him with Veronica. Her worship of John as a perfect man shattered. She planned the murder using two revolvers, inspired by a detective novel explaining that ballistics could match bullets to specific guns. She shot John with one and hid it, then stood holding the other so the mismatched evidence would deflect suspicion.
Poirot arrives, having followed Henrietta. Gerda brings tea and the workbag containing the cut-up holster. Poirot quietly moves Henrietta's teacup back onto the tray. Gerda drinks from the cup, which contains poison she intended for Henrietta, and dies.
Henrietta reveals the full scope of her cover-up, undertaken because John's dying word was not an accusation but a plea to protect Gerda, whom he loved in his way. Henrietta found the murder weapon where Gerda hid it, concealed it inside a clay horse sculpture in her studio, obtained a stranger's fingerprints on it, and planted it in Poirot's hedge. She drew Ygdrasil in the pavilion to direct suspicion toward herself. The Angkatells understood and helped, with Lady Angkatell's misdirections deliberately steering Inspector Grange away from Gerda. Poirot calls Henrietta one of the best antagonists he has ever faced.
Back in London, Henrietta visits Mrs. Crabtree at the hospital and urges her to keep fighting for John. Alone in her studio, grief breaks over Henrietta. But as tears fall, she envisions a veiled figure in alabaster, sorrow hidden beneath drapery. She cannot grieve as a whole person; she must channel loss into creation. She whispers: "John, forgive me, forgive me, for what I can't help doing."