It had been hard not to assume the midnight call dispatching Kathryn Oliver to the Santa Marcel Intermodal Rail Facility was some sort of informal departmental hazing ritual for the newly minted Senior Detective the very evening she'd been celebrating the retirement of her mentor. Poking around shipping containers in the middle of the night is the last thing Kate wants to do, especially when it means trying to validate a tip to the human trafficking hotline. Finding two dozen young women recently freed from a locked trailer should have been a win for the forces of good, but the gruesome body discovered among them - and the shadowy form glimpsed escaping the scene - changes the focus of Kate's investigation. Despite the women's assurances that the enigmatic figure poses no threat and is, in fact, an ally, Kate remains fixated on tracking down what she believes to be her most promising suspect for the murder.

The leads are thin, but one takes her to the offices of Vasquez Industries and an unexpected reunion with the high school boyfriend who dumped her at the Senior Prom. Blinded by the searing pain he awakens deep within her soul, Kate eschews the offer of assistance the powerful shipping magnate could provide and resolves to soldier on alone. It's not long before she realizes burying herself in the case buys her little comfort from the memories of another time she can no longer ignore.

When Kate's chief suspect unexpectedly alights on her garden wall bearing an explanation more appropriate to ancient Mesoamerican civilizations than modern Southern California, the entire case takes on an urgency she never expected. Short on clues and under pressure also break up the human smuggling ring before they can make another shipment, Kate reluctantly joins forces with the masked vigilante with the hope of tying him to the murders - and instead finds herself pulled into a world where the lines between reality and mythology are irrevocably blurred.