When a Russian bomber crashes in the South China Sea, the covert special-ops soldiers of Section 20— Thomas “Mac” McAllister, Samuel Wyatt and Gracie Novin — are sent to investigate. There, they cross paths with Katrina Zarkova, a rogue Russian operative with questionable loyalties. Under orders of the new commanding officer, Col. Alexander Coltrane, Section 20 pursues stolen contents of the Russian jet across Southeast Asia. They will work alongside the Malaysian police to shut down a Triad gang in Kuala Lumpur, uncover a corrupt plot by a wealthy Indian businesswoman running for Parliament and plunge into the jungles of the Golden Triangle in Myanmar, facing off against mercenary drug agents and terrifying warlords as they uncover a conspiracy that threatens to push the world to the brink of global conflict.
Reuniting for what they think is a routine "cleanup" exercise in Malaysia, Gracie Novin, Samuel Wyatt and Thomas "Mac" McAllister learn that a British operative in possession of intel about a downed Russian plane has been killed in Kuala Lumpur.
Section 20 forges an uneasy alliance with Zarkova in hopes of tracking down a stolen nuclear warhead in Kuala Lumpur; the group grows frustrated when Police Inspector Amy Leong pulls them off the job after a false alarm.
Section 20's search for the missing nuclear warhead leads them to India, where three scientists have been kidnapped by a militant; the team gains valuable intel on Anjali Vartak, a rich Hindu with a personal vendetta against Muslims.
As Wyatt is tortured by Vartak's henchmen, Mac presses her corrupt lawyer to hand over an encrypted hard drive that might hold clues to the whereabouts of a pair of "nuclear suitcases."
Following a high-speed jungle ambush in Myanmar, the suitcase nukes end up in the hands of a brutal Rwandan drug lord with a jealous streak; Colonel Beshnov, the Russian Alpha Group leader, surprises Pavel with a revelation about Zarkova.
Novin and Zarkova find themselves at the mercy of corrupt police, while Mac and Wyatt take temporary refuge in a local village; Coltrane finally learns the location of the suitcase nukes, but the revelation comes at a high price.
As Wyatt convalesces, Coltrane, Mac and Novin embark on a covert, 24-hour mission inside Russia to extract an FSB analyst with potentially vital information. Katrina questions Pavel's true identity, but chooses to stand by her commanding officer.
Coltrane defends his decision to go rogue with S20. After tailing Hassan and the nuclear suitcase to a deserted shopping mall in Jakarta, Wyatt and Novin face down threats from Komodo soldiers and, later, Colonel Aldo and his insurgents. As Katrina weighs her allegiances, Pavel resets the parameters of the Russian plans to overthrow the Indonesian government.
In pursuit of Pavel, Section 20 clashes with two other Russian renegades, Natasha Petrenko and Artem Orlov, as they attempt to purchase sophisticated software designed to short-circuit a ghost satellite containing precious cargo. After a brief respite with his wife Madison, Wyatt takes a temporary security job working for an obnoxious military-tech tycoon, Caleb Montgomery, but soon finds himself thrust back into the danger zone.
Section 20 faces an ultimate dilemma as it battles Pavel and his team of Russian turncoats for keys to Soviet-era missiles thought to have been destroyed years earlier. The conflict takes S20 from a remote village in the Philippines to Saloglu, Azerbaijan, where three long-range missiles are ready to be fired on major cities in the West. Can the team stop Pavel and save the world from Armageddon?