The Fourth Arm

The French Resistance spot a new German weapons base being developed near Calais. Their sabotage attempt goes badly wrong while a Bomber Command mission also proved unsuccessful. SOE decide this needs a trained unit.

Returning from France, Gallagher begins to compile a team of specialists to train for a one-off mission behind enemy lines. Not everybody is convinced that some can be trusted to follow orders.

Gallagher hands over his new unit to Lt. Col. Squires to begin their training. Scientist Stephen Lovell might be the most vital person on the mission but the army intend to play hardball with him.

Training intensifies with the unit put under extreme interrogation methods to see how they fare. Macaulay's attempted night out becomes a cropper.

The date of the mission is pushed forward when SOE receives new intelligence that the Germans could have up to 14,000 rockets. Final selection is held before paratroop training begins in earnest.