Detective and former Marine Capri Crawfeld boards The Bountiful Pearl, a boutique culinary cruise, hoping to leave police work behind and reconnect with her husband. Then a former model vanishes after a night at the martini bar. Everyone else calls it suicide. Capri isn’t so sure.

Two more deaths follow, and a pattern of poisoning emerges. Scrambled Nietzsche quotations appear on the victims’ social media. Access logs are falsified, surveillance footage is altered, and every lead points to an innocent passenger.

The killer is a cybersecurity prodigy who has appointed himself judge of the unfaithful and the corrupt. When he notices Capri closing in, he starts sending her anonymous texts that are taunting, personal and meant to mislead.

What began as a vacation becomes a battle of wits with a killer determined to prove himself superior. To stop him, Capri will have to understand him without becoming like him.