Mercy Brennan followed in her father's footsteps in a law enforcement career, but she has no interest in any other connection to him. A US Marshal in St. Louis, Missouri, she's assigned to a joint task force with the St. Louis PD that puts her back into contact with her father and in the sights of St. Louis's most powerful gang. When the gang has reason to believe Mercy has possession of some highly sensitive and incriminating information, her boss assigns Mark St. Laurent - a Deputy US Marshal and Mercy's ex-boyfriend - to get her out of town.

Kaely Quinn's talents as an FBI behavior analyst are impossible to ignore, no matter how unorthodox her methods. But when a reporter outs her as the daughter of an infamous serial killer, she's demoted to field agent and transferred to St. Louis. When the same reporter who ruined her career claims to have received an anonymous poem predicting a string of murders, ending with Kaely's, the reporter's ulterior motives bring his claim into question. But when a body is found that fits the poem's predictions, the threat is undeniable.

Police officer Isabelle St. John loves her crazy, loud law-enforcement family. And she knows they'll be there for her when things get tough. Like when her partner is murdered and she barely escapes with her own life. Determined to discover exactly what happened, Izzy's investigation sends her headfirst into a criminal organization, possibly with cops on the payroll - including someone from her own family. With her dead partner's handsome homicide detective brother Ryan shadowing her every move, Izzy's head is spinning.

Honorably discharged from the Army after an explosion nearly killed her, former military psychiatrist Brooke Adams has set up shop to help others - but her days of helping military personnel are over. She's got her own battles to fight from her time overseas, and she's not equipped to take on more. Former Army Special Ops Sergeant First Class Asher James could handle anything war sent his way - terrorists, bombs, bullets. The only thing that scares him now is sleep. Finally convinced that he needs help, Asher makes an appointment with a counselor.

Jake Silver may not be able to put the memories of his time as a sniper and Navy SEAL behind him, but at least he can put his skills to use as a part of the Jones Inc. rescue team. Saving the life of pediatric heart surgeon Dr. Aria Sinclair on Denali helped, too. Now, he can't get her out of his head, and when he hears she is in the path of a hurricane down in Key West, he can't help but jump on a plane to rescue her.