The members of covert antiterrorism unit Section 20 are reunited by commanding officer Coltrane under the pretence of rescuing Dr. Helen McCluskey, a biochemist who's been taken as a hostage in Kosovo by the Albanian mafia.

After catching wind of a feud between Edon and his son Loric, S20 launches a raid on their business in hopes of extracting the location of the bioweapon. Loric's self-serving cooperation leads them to an exchange between Edon and jihadist brothers Zayef and Mahir.

S20 finds itself in Tel Aviv, where Kogan has escaped with a deadly piece of military tech that he plans to sell to Zayef and Mahir. The device, however, winds up in the hands of a notorious Israeli gangster who promises to make matters even more complicated.

Novin is forced to cooperate with Topal and Danny. After an explosive stand-off with Zayef and Mahir, Spiegel threatens to blow the lid off S20's operations in Tel Aviv, and later, the squad's arrangement with the local police reaches its tipping point.

S20 raids Zayef's hideout, leading to a confrontation that finds Mac defying orders to keep his team safe. Suspecting that Zayef plans to deploy the stolen military tech during a UN conference in Munich, S20 heads west, where a showdown of epic proportions awaits.

Long after the incident in Munich, Wyatt and Novin reunite with Mac who has since left the military; but while he lives out a seemingly idyllic existence with his wife and daughter, his violent past - and fears that his service was inadequate - haunt him.

Spencer joins S20 to take down Zayef for good, but when intel leads them back to the Demachi's, S20 finds itself embroiled in a feud that may expedite Zayef's plans and place military-grade weapons in the hands of terrorists across Europe.

S20 plans to storm a freighter carrying weapons, but when Spencer administers a kill order, Coltrane grows suspicious. As members of S20 contemplate following their conscience, Zayef divulges intel that could drastically change their fate.

With Chetri in the wind and Carolyn on their tail, Novin, Wyatt and Coltrane are forced to weigh loyalty against duty and self-preservation; still blacklisted and left with scant resources, S20 seeks the help of Russian allies to combat Russian foes.

After receiving shocking intel from an unlikely Russian informant, S20 decides to reunite for one final mission to track down Arianna and avenge their comrades. This time, however, they're doing things a little differently.

Stonebridge, Scott and the S20 team get more than they bargained for when, on the eve of a historic nuclear-weapons summit, the British Ambassador to Thailand learns that his daughter has been kidnapped by a ruthless Bangkok gang led by an expatriate named Ray McQueen.

Locke and Section 20 regroup with Scott and Stonebridge tasked to bring in McQueen. The boys soon realise that Chloe's kidnapping is the tip of a much larger plot, one involving a North Korean crime syndicate, Office 39, and its ruthless Bangkok leader, Lee Dae-Ho.

Shiro, son of the Yakuza crime syndicate boss, ascends to power with the help of a duplicitous Lei, and vows revenge for his father's murder. While Section 20 fends off waves of attacks from the Yakuza, Scott's long-anticipated visit with son Finn is less than idyllic.

Hoping to track down Yakuza's shipment of vanadium, Scott strikes a deal with a pair of bounty hunters looking to kill Shiro. Having put his son on a bus to safety, Scott rushes off to rendezvous with his mates, who have closed in on Shiro and Mei in Southern Thailand.

Scott and Stonebridge cross the North Korean border in hopes of spoiling a nuclear-weapons celebration. Mission accomplished for now, Mei returns home and reunites with an old flame. In Bangkok, Finn chats with the wrong stranger and ends up running for his life.

In North Korea, Li-Na (aka Mei) is tasked by her mentor Moon Young-Su to pry a confession out of Scott & Stonebridge, using Finn as leverage. Meanwhile, Locke & Martinez recruit a familiar face in Russia to help get them into North Korea and attempt a rescue operation.

In Vienna, the phone of a Russian mobster, leads S20 to a rendezvous between Kwon and a bomb maker - a man Locke dearly wants to apprehend. Later, Scott and Stonebridge crash a bank heist in search of a document that holds the key to Kwon and Li-Na's diabolical plans.

With Nina's assist, Scott & Stonebridge track down an eccentric young encryption analyst hired by Kwon & Li-Na to access vital nuclear-material codes. Later, Locke comes face-to-face with his nemesis, while Scott & Stonebridge intercept the interceptors of a key convoy.

On the trail of Li-Na and Kwan, Stonebridge and Scott play a hunch and head to Geneva where a nuclear disarmament conference is taking place. A faceoff between Section 20 and the North Korean renegades ends in a flurry of gunfire... and an inconceivable betrayal.

Gone to ground, Scott and Stonebridge try to elude a team of mercenaries in the Swiss Alps in order to bring a traitor to justice. With their ammo nearly spent, the boys get a helping hand from an unexpected source before ending up in a final, epic fight to the finish.

Section 20's Samuel Wyatt, Thomas "Mac" McAllister and Gracie Novin are reunited for a dangerous mission in Malaysia after a Russian plane with precious cargo crashes under suspicious circumstances.

Section 20 forges an uneasy alliance with Zarkova in hopes of tracking down a stolen nuclear warhead, but find their efforts undermined from within.

Section 20's search for the missing nuclear warhead leads them to India, where a powerful woman with a vendetta is linked to the weapon's heist.

Desperate to locate a pair of "nuclear suitcases", Section 20 leans on a corrupt lawyer - and on Zarkova - to crack an encryption code and lead them to a rendezvous with Vartak and Gopan.

After the suitcase nukes are stolen by a brutal drug lord in Myanmar, Section 20 rush to the Punchan Province in a desperate attempt to prevent him from selling them to a nefarious buyer.

After several close calls in a prison and at a local village, Section 20 finally closes in on the stolen nuclear weapons - but will they be able to wrest them from Zaza and his soldiers?

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.

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.

Section 20 faces an ultimate dilemma as it battles Pavel and his Russian turncoats for keys to Soviet-era missiles. The conflict takes S20 from a remote village in the Philippines to Saloglu, Azerbaijan, where long-range missiles are ready to be fired on the West.

The man behind some of the worst terrorist attacks on the West escapes during a prison break masterminded by his British wife. Anti-terrorist organisation Section 20 is resurrected and an all new member unit set out on a life-or-death mission across the ME and Europe.

Section 20 start to close in on terrorist Omair Idrisi and his wife Jane Lowry, but the team is forced to extract devious arms dealer Morgan Ives from Libya.

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.

Things aren't looking good for Mac. He's blown his cover and is now facing certain death. Donovan digs into Zarin's past... and she doesn't like what she learns.

Section 20 must stop Lowry and Dr. Markov from making and unleashing a deadly chemical weapon. In desperate need of intel, Novin infiltrates a drug lord's home.

Lowry calls on a young jihadi to unleash the deadly gas in a busy airport, while Reynolds is forced to make a life-defining decision as Section 20 races to prevent the attack.

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

Jensen starts to delve into Project Tenebrae, while Mac and Wyatt head to the black site where Idrisi is imprisoned to break him out before Lowry gets to him.

The team run into trouble as they race to get Idrisi back across Europe. The surprises keep coming as they learn the truth about Jensen and Project Tenebrae.

Section 20 are desperate to clear their names; and to do so, they hatch a big and reckless plan.