John Porter leads his unit into battle trying to rescue the CEO of a British weapons manufacturing company captured in Iraq, just before the invasion started. His team is joined by Hugh Collinson, operative of British military intelligence. The operation almost goes awry when Collinson kills larger portion of Porter's team, and blames a teenage suicide bomber, As'ad, Porter previously saved. The surviving members of the team manage to rescue their target, and Porter rejects Collinson's offer to joint Section 20, a new unit within military intelligence, doubting Collinson's account of the rescue operation incident and resigns from the SAS.

Leatherby takes Kamali's daughter, Ester, hostage. Section 20 attempts a brazen rescue mission to get her back. Dalton tortures and interrogates Sofia for information. The escape ruse that Kamali and Dalton use has surprising consequences.