The chill of a San Francisco summer can be deadly. No one knows this better than Capri Sanzio, who makes her living giving serial killer tours of the city. Capri has been interested in the topic since she was a kid, when she discovered she's the granddaughter of serial killer William 'Overkill Bill' Sanzio. She's always believed in his innocence, though she's never taken the leap to fully dive into the case.

But now an Overkill Bill copycat has struck in San Francisco. And Capri's former mother-in-law, Sylvia, just cut off Capri's daughter's tuition payments. Needing cash, Capri wonders if this is the time to exonerate her grandfather. The case is back in the news and the police will be looking to understand the past to catch a present-day killer. Capri could finally uncover the truth about Overkill Bill--documenting the process with a podcast and a book--and hopefully earn some money.

Before Capri can get very far, the cops discover the copycat's latest victim: Sylvia. Capri soon finds herself at the heart of the police's investigation for an entirely different reason. She and her daughter are prime suspects.