Enjoying a long-deserved vacation, Scott (Sullivan Stapleton) and Stonebridge (Philip Winchester) 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
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 (Rhona Mitra) looks for the source that exposed her team in Beirut, but discovers a surprising ally and a piece of al-Zuhari's plan.
Although they are uncertain of others' loyalties, the team must work with an asset in Beirut to get a lead on James Leatherby (Dougray Scott), a dangerous and unpredictable operative with ties to al-Zuhari.
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.
While recovering from a shocking turn of events, Section 20 faces a different threat: a new enemy joining forces with an old one. Locke (Robson Green) draws Kamali (Zubin Varla) in closer to the team. Scott (Sullivan Stapleton) looks for an old friend, while Stonebridge (Philip Winchester) gets closer to a new one.
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.
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.
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 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.
Scott and Stonebridge face a new key player in Al-Zuhari's plan; the team resorts to questionable measures, sparking conflict within the unit.