After a disastrous failed hand-over from a independent Syrian liberation army unit, of the terrorist, "Omair Idrisi", Sergeant Daniel "Mac" Macallister, is imprisoned facing a court marshal for hitting his superior officer. Because of the failed hand-over mission, Col. Adeena Donovan, MI6, re-establish the disbanded "Section 20" unit. Mac, is offered a chance to join this new unit. He is quickly set on mission to recruit "Sergeant Samuel Wyatt", a deniable American operator, in captivity by General Farid. During the rescue/recruit mission, other new "Section 20" operators shows their value as members of the new team. The team is assembled in Tripoli, for a mission to capture Idrisi and as well reveal his source of money, Khalid, who transferred 5 million just before the team intervened. The team take custody of Khalid, but Omair eludes capture with help from his wife. Omair phones Mr. Ives, who is an arms dealer with the weapons for sale Omair intends to buy for the money.

Mac, Wyatt and the gang pursue Idrisi and his radicalized British wife. They seek to track him down via an arms dealer who just made a delivery to the cell leader, and was shot down by the same to get rid of loose ends. The crew from Section 20 rescues the arms dealer to find out what weapons he delivered and where Idrisi is. Later, when attacking Idrisi's compound, the US military gets involved, launching a bunker buster missile and putting the team in harms way.

As Jane Lowry surfaces in Budapest, Mac and Wyatt are forced to go undercover to infiltrate a dangerous group of white supremacists that has something she needs.

Mac and Dr. Markov are taken by white supremacist Josef and Rosa Varga to a secret militia base. Jane Lowery targets Col. Donovan. Wyatt whines about being stabbed. Section 20 takes bold steps rescue Mac and Markov.

With Markov taken by Jane Lowry, Section 20 track them down to a drug lord's mansion. Section 20 carry out a plan to stop Lowry and Markov from unleashing a deadly chemical weapon or the whole world will be at their demise.

Lowry and Borisovich continue their cat and mouse games with each other and with Section 20. As 20 closes in on Lowry and Markov, Lowry initiates a plan to set off a device in an airport. Reynolds emotes about her actions.

It's Section 20 v Jane Lowry in a race to get to Omair Idrisi. It's a mission that hurls comms officer Jensen into extreme danger.

As Lowry makes her play to rescue Idrisi from the Col. Parker's black site, Section 20 races to get him first. Jensen stoically recovers from his wounds. Reynolds continues to believe Donovan is hiding something important to the mission.

The team learns about Colonel Donovan's involvement in Project Tenebrae. Waves of PMC soldiers trying to recapture Idrisi have a running, driving, and shooting battle with Section 20. Donovan and Lowry have another face to face encounter.

The Russians are coming. Ives loses Idrisi to Russian agents. Twenty goes after the Atlas of covert British agents that Lowry stole and later hid. Stonebridge and Scott's surprise return aids Section 20 in a bold plan.