Ep. 718: Mouri Kogoro investigates a suspected affair involving a mystery writer and her assistant.

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A mystery writer hires Mouri Kogoro to investigate potential romantic involvement between her husband and assistant. Kogoro, Ran, and Conan spend the night at a separate residence. Upon waking, they discover that all three individuals in the writer's home have died from poisoning. The husband succumbs first after consuming poisoned sleeping pills, followed by the assistant who drinks poisoned tea. The writer dies last after eating poisoned chocolate bars. Conan notices spilled water and two unopened chocolate bars in the writer's room garbage. The case is solved when it is revealed that the writer originally intended to stage a murder-suicide by framing her husband and assistant, but after finding them already dead, she accidentally consumes the poisoned chocolate bars intended for her own suicide.