San Francisco homicide detective Terry Eckhart has seen enough death to know when a crime scene is speaking directly to him.

When a body is discovered along the coast at a forgotten military battery, the murder appears isolated—until Eckhart realizes it mirrors two brutal killings from his past: a suspicious house fire that claimed Mary Quinn, and the ritualized murder of Janice Collins, found in the Sutro Baths with Eckhart’s name written onto her skin.

As Eckhart and his partner Nick Fowler dig deeper, a chilling pattern emerges—each murder is tied to prime numbers, dates and names chosen with mathematical precision. The killer, a ghost named Riley Richmond, is playing a long game—and Eckhart is at the center of it.

When Ally Wilder, the Assistant District Attorney and Eckhart’s estranged girlfriend, disappears, the hunt becomes a race against time through San Francisco’s most haunting landmarks—from the ruins of the Sutro Baths to Alcatraz and the abandoned missile silos of Angel Island.

With the body count rising and a final clue—17 is not the end—Eckhart must confront not only a brilliant, obsessive killer, but his own past mistakes, before the sequence reaches its final, deadly conclusion.

Because in Richmond’s world, perfection isn’t abstract.

It’s fatal.