When a driver slams his pickup truck into a tandem bike being ridden by Carlos Guzman and his fiancée, Tasha, it's more than a simple hit-and-run; the driver clearly intended to harm them. Undersheriff Estelle Reyes-Guzman gets the call with the news of her son's accident and wastes no time racing to his side. While Carlos struggles with critical injuries, an employee at the bike shop where Carlos bought the tandem is found shot dead in a dumpster --- the same man who had borrowed the truck that mowed down Carlos and Tasha. Not a believer in coincidence, Estelle pursues every possible angle with a cop's determination to solve the case, and a mother's resolve to keep her son safe at any cost.

Posadas County has enjoyed a surge in visitors, jobs and prosperity since rancher Miles Waddell used much of his inherited half billion to create an internationally renowned astronomy complex atop Torrance Mesa. Benefits include a narrow gauge train linking the village of Posadas to NightZone. A ripple of unease is felt across the county with the arrival of developer --- no, speculator --- Kyle Thompson. Why did he and his wife quietly purchase a large scrubby acreage to the north of NightZone? Unease grows with a drive-by shoot-up at the Posadas Register, its 25 shots wounding a reporter and the paper's editor. Sheriff Bob Torrez and Undersheriff Estelle Reyes-Guzman see a connection to NightZone...and worse, a connection with Torrez's own nephew. Why? And then murder strikes.

One blizzardy New Mexico night, Posadas County Deputy Pasquale picks up a toddler scooting his Scamper along the shoulder of State 56. Yes, it's horrifying --- a child apparently dumped out of a truck by his father. Nearly as horrifying is what unrolls while Christmas approaches after dad Darrell Fisher's arrest: a request arrives from the US Forest Service to locate a missing range tech and his unit last reported headed for nearby Stinkin' Springs, and the brutal murder of Constance Suarez in the border town of Regál, population 37. The Sheriff's Department is stretched to its limits as its dedicated personnel juggle working cases and caring for citizens with their own relationships and family celebrations.

A violent crash has occurred. Not only is the vehicle totaled and the driver and a passenger crushed inside, a dead boy has been ejected. The first deputy to join Undersheriff Bill Gastner at the scene is rookie Robert Torrez, the department's newest hire. Before Gastner can head him off, Torrez sees that the boy is his spirited younger brother. And the girl crushed inside the SUV is a younger sister. The driver of the Suburban, also dead, is the assistant District Attorney's teenaged son. Were the three dead kids running from someone --- or something --- rather than speeding? Further investigation reveals that a fourth teen should have been in the vehicle, but is now missing. Where had the four kids been? And why?