The story of the founding of the SAS in the heat of the North African desert in 1941. David Archibald Stirling is an aristocratic dreamer who has a vision for a new kind of war: attacking the enemy where they least expect it - from behind their own lines. Against the odds, Stirling helps the Allies towards victory in the desert but he loses Lieutenant Jock Lewes, his right-hand man.

Stirling's second in command is now Captain Mayne. An officer as unpredictable and dangerous as the new phase of war that is about to begin. The Germans are training special units to track, intercept and kill the marauding SAS. Disaster strikes when Stirling is captured by the Germans. As the SAS prepare to fight Hitler in Europe, they will be without the leadership of the man who created them.

Stirling is locked away in Hitler's prison. Leadership of the SAS passes to Paddy Mayne, a man who has built his reputation on the battlefield as a warrior. In 1943, the SAS leaves the desert for Europe to enter a darker theatre of war. They will face the terror of execution and the trauma of civilian casualties. And they will be the first to witness the nightmare of Belsen concentration camp.