Andre De Beers, a Belgian fighter pilot, is taken prisoner by the Gestapo and forced to watch his brother being tortured to death. De Beers overpowers his guard and escapes from Gestapo headquarters, seeking refuge with his old friend Alain. Determined to exact vengeance, he begins a campaign of killing German soldiers. After Kessler orders the capture and shooting of twenty innocent people in retaliation, Albert orders Alain to kill De Beers to stop any more bloodshed, however Monique and Natalie come up with an alternative solution. Albert is forced to stamp his authority on the others to preserve Lifeline’s safety when he learns that they have taken matters into their own hands. Meanwhile, as Kessler begins to launch an innovative new scheme to police Brussels, a communiqué from Berlin has shocking news for Brandt while sudden German radio silence indicates that a significant turn in the war is about to occur. The date is 6 June 1944.

At Gestapo headquarters, Kessler takes an instant dislike to the newly arrived Luftwaffe Major Hans Dietrich Reinhardt, who has joined him in a final concerted attempt to crush the evasion lines. As the Allies continue to advance from the invasion beaches, Lifeline must continue their efforts in getting airmen back to Britain, but when Natalie attempts to guide two evaders down to Spain, it becomes clear that their work may at last be over.

An assassination attempt has been made on Hitler, and Kessler believes that Reinhardt is involved in the conspiracy. He begins to gather information that he hopes will provide his colleague’s guilt. Meanwhile, Albert becomes aware that the Communists are once more out to get Lifeline, and that he is their target.

Bradley travels to the Ardennes to continue recruiting his own private army of former airmen to engage in sabotage activities – the target is V2 testing sites. Bradley’s first objective, however, is to hijack a convoy of weapons and he asks Monique for assistance in recruiting men and resources. Lifeline, previously an evasion network, is now a fully-fledged guerrilla operation

As Bradley’s army remains in hiding along the Dutch border, he and Natalie become closer as they work together planning the raid on the V2 site. To increase his chances of success, Bradley must try to obtain the rocket delivery schedule and plans to get the information by dining with Kessler at the Candide…. Meanwhile, Reinhardt is rapidly closing in on Lifeline, with Natalie as his chief suspect.

The Allied advance continues as they at last enter Belgium, and the Germans begin to plan a strategic withdrawal from Brussels. Albert is petitioning for his release from prison, while Bradley endeavours to forge links with other resistance groups. The people of Brussels are now left to their own devices, and recriminations are brewing for collaborators and black marketeers. Kessler comes to help Madeleine, while Alain offers Monique and Natalie a place to hide. Meanwhile, Reinhardt at last obtains proof that the Candide is Lifeline’s base of operations, and prepares to strike.

Albert is finally released from prison and reunited with Monique. The Lifeline personnel continue to be in danger of reprisals from their own people and the Communists for alleged collaboration with the Germans, but Albert refuses to leave the Candide. The Allies are still making their way towards Brussels, and Natalie and Alain join the offensive. As Kessler and his men leave the city, Reinhardt stays behind to complete his investigation into Lifeline and pays one last visit to the Candide, just as Paul Vercors emerges to take ultimate revenge on Albert.