Mercer Broderick is haunted by the death of his wife and son. While on a covert mission as a CIA operative four years earlier, he'd been on foreign soil instead of protecting Keara and Braeden in America. His family's killers were never found. With his entire world destroyed, he quit the CIA and struggled for a reason to live, wallowing in grief and an all-consuming guilt.
Mercer emerged from the fog of devastation, obsessed with swift justice and driven to honor the memory of his beloved wife and child. He forged a network of wealthy benefactors across the world—the Alliance—influential, high-powered people who secretly yearn for a new world order of vigilante justice. With the support of a mysterious Danish woman, Eva Henriksen, Mercer built Zion in the mountains of Wyoming, a fortified sanctuary for his handpicked team.
After Mercer gets a lead on who ordered the hit on his family, he's drawn to El Paso to take on the Ruiz cartel and the faceless man known only as the Panther. Accompanied by his exotic bodyguard specialist, Keiko Kayakova—a blue-eyed Japanese beauty trained by her lethal Russian father—Mercer calls upon the Sentinels to join his Alliance team—Detective Mateo Vega, computer genius Axel Ballard, Liam Walker, and Jake Dunkirk. With the clock ticking, Mercer must take down the Panther before he closes up shop and disappears forever, taking his fortune and leaving a bloody carnage of dead witnesses.
But when his plan derails, Mercer is forced to risk his life to stop a mad man from getting away with murder.