A series of murders in New York City has stymied the police and FBI alike, and they suspect the culprit is a single killer sending an indecipherable message. But when the two federal agents assigned to the investigation are taken out, the FBI takes a more personal interest in the case.

Special Agent Ty Grady is pulled out of undercover work after his case blows up in his face. He's cocky, abrasive, and indisputably the best at what he does. But when he's paired with Special Agent Zane Garrett, it's hate at first sight. Garrett is the perfect image of an agent: serious, sober, and focused, which makes their partnership a classic cliche: total opposites, good cop-bad cop, the odd couple.

They both know immediately that their partnership will pose more of an obstacle than the lack of evidence left by the murderer. Practically before their special assignment starts, the murderer strikes again - this time at them. Now on the run, trying to track down a man who has focused on killing his pursuers, Grady and Garrett will have to figure out how to work together before they become two more notches in the murderer's knife."

Six months after nearly losing their lives to a serial killer in New York City, FBI Special Agents Ty Grady and Zane Garrett are suffering through something almost as frightening: the monotony of desk duty. When they're ordered to take a vacation for the good of everyone's sanity, Ty bites the bullet and takes Zane home with him to West Virginia, hoping the peace and quiet of the mountains will give them the chance to explore the explosive attraction they’ve so far been unable to reconcile with their professional partnership.

Ty and Zane, along with Ty’s father and brother, head up into the Appalachian mountains for a nice, relaxing hike deep into the woods where no one will hear them scream. They find themselves facing danger from all directions: unpredictable weather, the unrelenting mountains, wild animals, fellow hikers with nothing to lose, and the most terrifying challenge of all. Each other.

Special Agents Ty Grady and Zane Garrett are back on the job, settled into a personal and professional relationship built on fierce protectiveness and blistering passion. Now they're assigned to impersonate two members of an international smuggling ring-an out-and-proud married couple-on a Christmas cruise in the Caribbean. As their boss says, surely they'd rather kiss each other than be shot at, and he has no idea how right he is.

Portraying the wealthy criminals requires a particular change in attitude from Ty and Zane while dealing with the frustrating waiting game of their assignment. As it begins to affect how they treat each other in private, Ty and Zane realize there's more to being partners than watching each other's backs, and when the case takes an unexpected turn and threatens Ty's life, Ty and Zane will have to navigate seas of white lies and stormy secrets, including some of their own.

Baltimore, Maryland, is a city in alarming distress. Rising violence is fanning the flames of public outrage, and all law enforcement agencies, including the FBI, are catching blame. Thus the FBI's latest ideas to improve public relations: a municipal softball league and workshops for community leaders.

But the new commitments just mean more time Special Agents Ty Grady and Zane Garrett have to spend apart when they're happily exploring how to be more than by-the-book partners. Then the latest spate of crime explodes in their faces-literally-throwing the city, the Bureau, and Ty and Zane's volatile partnership both in and out of the office into chaos.

They're hip-deep in trouble, trying to track down bombers and bank robbers in the dark with very few clues, and the only way to reach the light at the end of the tunnel together requires Ty and Zane to close their eyes and trust each other to the fiery end.

Special Agents Ty Grady and Zane Garrett have managed the impossible: a few months of peace and quiet. After nearly a year of personal and professional turmoil, they're living together conflict-free, work is going smoothly, and they're both happy, healthy, and home every night before dark. But anyone who knows them knows that can't possibly last.

When an emergency call from home upsets the balance of their carefully arranged world, Ty and Zane must juggle family drama with a perplexing crime to save a helpless victim before time runs out. From the mountains of West Virginia to a remote Texas horse ranch harboring more than just livestock and childhood memories, Ty and Zane must face their fears--and their families--to overcome an unlikely enemy and bring peace back into their newly shared world.

After having their faces plastered across the news during a high-profile case, FBI Special Agents Ty Grady and Zane Garrett have become more useful to the Bureau posing for photo ops than working undercover. Just as Zane is beginning to consider retirement a viable option, Ty receives a distress call from a friend, leading them to a city rife with echoes from the past. New Orleans wears its history on its streets, and it's the one place Ty's face could get him killed.

Surrounded by trouble as soon as they land, Ty and Zane are swiftly confronted with a past from which Ty can't hide — one with a surprising connection to Zane's. As threats close in from all directions, both men must come to terms with the lives they've led and the lies they've told. They soon discover that not all their secrets are out yet, and nothing lasts forever.

Home from their unexpected deployment, the former members of Marine Force Recon team Sidewinder rejoin their loved ones and try to pick up the pieces of the lives they were forced to leave behind. Ty Grady comes home to Zane Garrett, only to find that everything around him has changed-even the men he went to war with. He barely has time to adjust before his brother, Deuce, asks Ty to be his best man. But that isn't all Deuce asks Ty to do, and Ty must call for backup to deal with the business issues of Deuce's future father-in-law.

Nick O'Flaherty and Kelly Abbott join Ty and Zane at the wedding on an island in Scotland, thinking they're there to assuage Deuce's paranoia. But when bodies start dropping and boats start sinking, the four men get more involved with the festivities than they'd ever planned to. With the clock ticking and the killer just as stuck on the isolated island as they are, Ty and Zane must navigate a veritable minefield of family, friends, and foes to stop the whole island from being destroyed.

It's been five years since Special Agents Ty Grady and Zane Garrett first worked together to solve the Tri-State murders, and time has been both harsh and kind. Engaged now, they face the challenge of planning a deeply uncertain future together. Zane is at the pinnacle of his career with one last mystery to solve, while Ty is at sea in a world where he's no longer the tip of a spear.

There's just one more hurdle in the way of their happy ever after: a traitor from their inner circle who threatens to burn their world to the ground. Squeezed between the Vega cartel, an unknown mole, and too many alphabet agencies to count, Ty and Zane must gather all their strength and resources to beat the longest odds they've ever faced. To make it out alive, they'll need help from every friend they've got. Even the friends who might betray their trust.