It's a baptism by fire when new recruits Jamie Dow and Alex Leonard join the SAS's elite fighting force team. Hot on the heels of an explosive hostage-rescue exercise in the regiment's Killing House, Red Troop led by charismatic Sergeant Henno Garvie is called to take command of a bank siege. This time the life or death situation is dramatically and tragically real.

As Red Troop bury Sam Leonard, a gunman shoots at a prominent European banker using an awesomely powerful sniper's rifle. He misses and the SAS are scrambled to find the gun and the British anti-globalist group suspected of carrying out the shooting. Jamie infiltrates the eco-warriors, convincing them of his skills as a sniper. But when things go wrong, it's not just a banker's life that is threatened.

Ten hopeful recruits to the SAS face their final and toughest challenge yet - a three-day combat survival course in the Welsh mountains, where they must evade capture by 40 Paras while navigating rough terrain and swollen rivers. Mick Sharp hopes to join his mate Jamie in the regiment, but Henno is out to make life difficult for him. But when two soldiers are found dead, it appears an even greater danger lurks in the woods.

Red Troop is called to a pharmaceutical laboratory after three Chechens break in to an area where scientists are working on a vaccine for a deadly form of anthrax. The gang threaten to release the anthrax, killing thousands, unless they are given money. Caroline gains access by posing as a doctor but Henno is captured and shot. Is blowing up the building and everyone inside it the only solution?

Jamie is kidnapped during a violent ambush in Northern Ireland while impersonating Bill Gracey, a politician whose life is in danger. Henno is furious, knowing his protégé faces torture and likely death. Breaking orders, he heads off into the Republic with Caroline in search of Cullen, a republican double agent, while Jem and Twamley do some digging of their own. Can they find Jamie before time runs out?

Henno and Twamley are kicked out of the regiment, despite saving Jamie's life in Ireland. The others, under Johnny Bell's command, are sent on a classified mission to Bosnia to 'lift' wily war criminal Glasnovic. To their surprise, Henno and Twamley are also there, training militia men. Reunited, Red Troop close in on Glasnovic but the blood bath leaves one of them fighting for their life.