Scott and Stonebridge face a new pivotal player in Al-Zuhari's plan, and with an imminent attack looming, the team resorts to questionable measures, sparking conflict within the unit.

Scott and Stonebridge are stranded in the Alps with the mercenaries in pursuit. Scott knows that the CIA hide weapons caches across Europe, so they find a telephone at the farm of a retired Austrian soldier Oscar (Wolf Kahler) to call Christy Bryant (Stephanie Vogt), a past acquaintance from Vengeance, for the location of the nearest one, at a nearby dam.

Enjoying a long-deserved vacation, Scott and Stonebridge are recalled after a fellow Section 20 member dies while pursuing the elusive terrorist al-Zuhari in Beirut. A new lead sends them into the remote jungles of Colombia in pursuit of a known associate of al-Zuhari’s and deep in territory controlled by a powerful drug cartel.

Scott and Stonebridge try to keep their promise to protect Ester; Richmond and Martinez follow an Al-Zuhari associate; the team sets out to stop an infiltrator before he reaches a populated area.

The daughter of Thailand's British ambassador is kidnapped, so Stonebridge, Scott and the rest of the team sign up for another do-or-die trying adventure.

Locke takes Section 20 off the radar, as they defy Whitehall to travel to Geneva where he is convinced that Li-Na and Kwon are preparing to attack the United Nations HQ.

Out of options and hunted by the resourceful cartel, Section 20 goes for a longshot and attempts an assault in downtown Bogota, hoping to obtain intel on one of al-Zuhari’s key people. Meanwhile, Dalton looks for the source that exposed her team in Beirut, but discovers a surprising ally and a piece of al-Zuhari’s plan.

Section 20 attempts a risky rescue for a potential new ally. Now veering close to the edge, but determined to find the truth, Dalton goes AWOL with a detainee.

Section 20 is torn between devoting their resources to the mission or saving one of their own. Stonebridge's health continues to affect him in the field. Al-Zuhari's network moves forward quickly, striking close. Kamali explains why yet another threat is emerging.

Scott looks for an escape from Black Bear Prison, while Locke becomes suspicious of Kamali. The team races to locate Stonebridge, whose condition grows more dire when he encounters Al-Zuhari's plan firsthand. Continuing his vendetta, Ulyanov closes in on Scott and Stonebridge.

Scott has a serious talk with his son whilst the rest of Section 20 form an uneasy alliance with a couple of CIA mercenaries as they go after Shiro and Mei Foster.

In the season finale, Stonebridge and Scott are in a race against time to find a pair of suicide bombers targeting Budapest.

Knox extricates a political leader from a Zimbabwe prison, and the unit tries to catch up with the escapee by tracking his activist daughter.

Locke works out that his long-time friend is working with the dangerous Yakuza and Office 39. Scott needs protect his son after they find themselves enemy fire.

After locating the terrorist safe house Katie is being held in, Porter is also taken prisoner, and Hugh Collinson and a team at Section 20 have to act quickly before it is too late.

In order to stop Knox, Scott comes to Bryant for assistance. Meanwhile Stonebridge has trouble focusing on the mission as he is bent on revenge. Section 20 get assistance from South African police to stop Knox's plot.

While recovering from a shocking turn of events, Section 20 faces a different threat: a new enemy joining forces with an old one. Locke draws Kamali in closer to the team. Scott looks for an old friend, while Stonebridge gets closer to a new one.

The team tracks stolen property to Russia, where Scott and Stonebridge continue their side careers as "outlaws." As Stonebridge's health continues to deteriorate, they discover new mysteries about a piece of Al-Zuhari's plan. Kamali worries that his cover identity may not hold.

Section 20 try to track down the real culprits behind the embassy attack, starting with getting information from gangster Ray McQueen.

The battle with Li-Na is now in Europe, as Section 20 look for a way to get back on her trail. Locke ends up getting an unexpected chance to confront his nemesis.

The team find out that Li-Na is planning to mount a nuclear attack in Europe. Locke puts himself in the firing line after he neglects the mission in order to avenge his son's murder.

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.

Porter and Masuku become the hunted as a bushman tracker leads the relentless Zimbabwean authorities after them, and Layla Thompson becomes increasingly aware of the tension that exists between Porter and Collinson.

Porter's life is in danger when he finds himself trapped in a rebels' base in Pakistan. When he manages to escape, he learns that Hugh Collinson, the man he blames for the fatal hostage extraction of 2003, has arrived in Afghanistan to meet him for a final showdown.

In Kosovo, Stonebridge, Scott and four hostages find themselves in dire straits after being double-crossed by KFOR soldiers and the drug lord Hasani.