On his last combat deployment, Lt. Cmdr. James Reece's entire team was killed in an ambush that also claimed the lives of the aircrew sent in to rescue them. But when those dearest to him are murdered on the day of his homecoming, Reece discovers that this was not an act of war by a foreign enemy but a conspiracy that runs to the highest levels of government. Now, with no family and free from the military's command structure, Reece applies the lessons that he's learned in over a decade of constant warfare toward revenge.

Alex Reeve - known as OPERATIVE 66 - is a former special-ops soldier and one of the UK's most lethal weapons. Previously a member of SC9, an elite covert unit with a remit to assassinate the country's enemies, Reeve was framed for treason and now lives a nomadic existence - as the merciless killers he once trained alongside hunt him down. For a chance of a normal life, Reeve must expose and dismantle the sinister SC9. So when a series of brutal killings in Germany have all the hallmarks of an SC9 tactic.

Court Gentry is known as The Gray Man—a legend in the covert realm, moving silently from job to job, accomplishing the impossible, and then fading away. And he always hits his target. But there are forces more lethal than Gentry in the world. And in their eyes, Gentry has just outlived his usefulness. Now, he is going to prove that for him, there's no gray area between killing for a living-and killing to stay alive.

A master assassin craves one thing above all else: a normal everyday life. Trained to be a killer from the age of 11, Peter has never known the things the average person takes for granted. He has always been an asset. Burned by the CIA and now occupying their secret hit list, he works overseas as a Ronin, living a solitary life in hiding. But someone knows where he is. A strange man arrives at his door offering Peter the chance of a real life. "Get this done and you can be free," he is told.

Waiting to be deployed on a critical mission, elite Marine Raider Matthew Redd stops to help a stranger and wakes up hours later to learn his team was wiped out in an ambush. Unable to remember anything, Redd can’t deny the possibility that he’s somehow responsible for the information leak that led to the massacre. He’s given a deal to avoid a charge of treason, but it means walking away from the Corps and the life he loved. As he faces his loss, Matty gets a cryptic message from his adoptive father, J. B.: “Trouble’s come knocking. . . . Might need your help.”