Former FBI agent turned full-time drifter, Karen Pantelli pursues a promising lead on her long missing mother to Orcas Island, Washington. Toiling as a hotel maid, she reaches a dead end until an encounter with an eccentric math professor raises a gruesome possibility. Her mother may have been murdered by a serial killer, the work of a cunning monster who has claimed hundreds of lives and evaded detection for decades by camouflaging his kills as accidents, suicides, or random acts of violence.

Aided by recent advances in artificial intelligence, the professor believes he can finally predict the killer's pattern. But then a stunning twist changes the game, propelling Karen across thousands of miles on a desperate mission to save innocent people before the trail goes cold forever.