Numbered drink cups at a barbecue backfires when mischief and poison are added to the mix. A writer is poisoned at a barbecue where the cups are marked with a number to identify whose is whose. The writer’s #5 cup and one of several #7 cups contain tainted bourbon from a pint bottle brought to the picnic by an elderly neighbor. Lieutenant James must sort it out and find the murderer. He uncovers some secrets about the writer victim, but a missing will, a closet drinker, and a college hazing incident provide important clues to the intriguing murder mystery.