FBI Hostage Rescue Team member Shane Livingstone is frustrated when an injury sidelines him during an operation to catch a sadistic killer. A killer who auctions off vicious ways to torture his victims and screens the events for money on the dark web. When a teammate dies during the op, a devastated Shane vows to track down the monster responsible—but to do so he’ll need access to specialized skills he doesn’t possess.

FBI Supervisory Special Agent Dominic Sheridan is an accomplished expert in the Crisis Negotiation Unit. Practiced, professional, used to dealing with high-stakes situations under tense conditions, Dominic is a master at manipulating people. Everyone, that is, but the headstrong rookie agent bent on destroying her fledgling career. As a child, Ava Kanas put her life on the line when the mob executed her father. Now someone has killed her mentor, the man who inspired her to become an FBI agent - and she’s the only one who recognizes it was anything but a tragic accident.

Former CIA assassin Alex Parker works for The Gateway Project, a clandestine government organization hell-bent on taking out serial killers and pedophiles before they enter the justice system. Alex doesn't enjoy killing, but he's damn good at it. He's good at dodging the law, too--until a beautiful rookie agent has him wondering what it might be like to get caught.

Forensic genealogist Rowan Healy has made a name for herself by helping investigators trace the family trees of violent criminals who have eluded justice for years. But the pressure of police cases left her burned out, and she’s shifted her focus to helping adoptees find their biological parents.

It should have been a routine investigation. Instead, DEA K-9 agent Adam "Deck" Decker watches in horror as one Denver hospital seems to be ground zero for overdoses of a new drug. Now Deck can only hope a certain ER doctor will help him and his canine partner track down the source. Dr. Tori Sampson has her reasons for not trusting federal agents, especially ones working for the DEA. But the rash of overdoses—including a heartbreaking case involving a teen—is alarmingly high. And the new opioid is not only extremely dangerous, it defies all the usual medical treatments.