Quick recap
At a friend's request, Miss Marple goes to Stonygates, the estate of her old school friend Carrie-Louise. Her husband, Lewis Serrocold, has turned it into an institution for young offenders, and the family lives among strange people. The fear is that someone is slowly poisoning Carrie-Louise. One night young Edgar Lawson makes a scene and fires a gun, and at the same moment her stepson Christian Gulbrandsen is shot dead. Two more deaths follow. Marple shows the scene was a conjuring trick: Lewis and Edgar, who is his son, staged it all to hide an embezzlement. Both die in the lake trying to escape.
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