Zaf infiltrates an AQ cell and attempts to turn a young Muslim extremist. Meanwhile Adam poses as an arms dealer in an effort to stop a thermobaric bomb falling into the terrorist's hands.
Adam is furious when he discovers that the bomb has already been sold to Zaf's cell.
The rest of the team soon discover that the mission is a suicide attack. Zaf, driving the van containing the bomb, has unwittingly become a suicide bomber. The race is on to intercept the moving vehicle and stop the bomb going off in central London.
Adam is forced to make a split-second decision to shoot a suspect who he believes is carrying the detonator. When he pulls open the dead man's jacket, he's relieved to see that he has got the right man.