When Philo Vance receives a note that harm will befall Lynn at the casino that night, he takes the threat seriously while the DA dismisses it. At the casino owned by Uncle Kinkaid, Lynn is indeed poisoned under the watchful eye of Philo. However, he recovers, but the same cannot be said for Lynn's wife Virginia, who is at the family home. Only a family member could have poisoned Lynn and Virginia and everyone has their dark motives. Philo will follow the clues and find the perpetrator.