Told to stand down after another failed operation, Lt David Stirling, an eccentric young officer, is frustrated with the military authorities' strategy. Stirling, along with fellow officer Lewes, plans to parachute men behind enemy lines.

While recovering in hospital, Stirling ruminates on Lewes' idea to attack the enemy from behind and hatches a plan to get approval for their unit from General Auchinleck at GHQ.

The newly recruited members of the SAS carry out a disastrous and devastating first mission. Determined to prove their strategy will work, they prepare to try again.

As the SAS's reputation spreads among the Axis Italian and German forces, another daring mission results in a shocking and devastating loss to the team.

Paddy initiates the Free French soldiers into some unorthodox training methods, and Stirling leads a raid on Benghazi accompanied by the prime minister's son, Randolph Churchill.

A meeting with Winston Churchill sees the SAS embark on their most daring operation to date. While success sees them achieve official status, Stirling receives some terrible news.