The team are alerted to a wave of possible British al-Qaeda attacks and receive a tip-off about an active terrorist cell. As Ben is sent on a dangerous undercover mission to infiltrate the cell, Harry is alarmed when Lucas claims he’s having flashbacks to the time he was locked in a Russian prison, and recalls the word ‘Sugarhorse’ being used by his captors.
Denying all knowledge of ‘Sugarhorse’, Harry secretly visits his trusted MI5 mentor, Bernard Qualtrough, who reveals that ‘Superhorse’ is a top secret MI5 operation, which the Russians have become aware of. Harry suspects there must be a mole within MI5 – but could there really be a traitor on the team?
Meanwhile, deep undercover, Ben discovers the terrorists are planning to bomb London and accompanies them on a ‘dry run’. But as he realises that it’s no practice and he’s just minutes away from innocent people being killed, Ros and the team face a desperate race to stop the bombs.
With four bombs about to go off, Jo refuses to let London be destroyed and puts herself at the centre of the situation…