Bittersweet Ending: Lifeline successfully remained hidden throughout the occupation of Belgium. But Monique has fallen out of love with Albert and moves to Britain, Natalie has lost both her parents and her two love interests, and the honourable Reinhardt is executed by a revenge seeking Kessler on trumped up charges. Kessler then escapes with his mistress.
Black and Grey Morality: Many of the Germans in this series are variously Punch Clock Villains or those who believe My Country, Right or Wrong. Even the nastiest character, Kessler the Gestapo chief has depth to his character. He is flawlessly sweet to his girlfriend, unlike Resistance leader Albert, who is quite ghastly to his. The various resistance groups argue among themselves and contain some rather nasty individuals. The Communists in particular are shown as backstabbers and Lifeline send British pilots home so they can continue bombing German cities. Lifeline also think nothing of killing a single mother in a hit and run before she could alert the German authorities to a hidden airman in series one.
British Brevity: Something of an aversion. While the show only ran for three seasons, those seasons were sixteen, thirteen, and fourteen (counting the unaired "What Did You Do in the War, Daddy") episodes, respectively.
California Doubling: Many Belgian set countryside scenes were filmed in Cambridgeshire due to the similarity of the landscape and the fact that the nearby tourist railway was home to a large number of 1940s period accurate European steam trains.
Christmas Episode: The Episode "Guests at God's table" in series two. It is also the episode in which Monique recognises and acknowledges the Moral Dissonance of their activities.
Code Name: Lisa's - and, later, Albert's - is Yvette.
Reinhardt is probably the most cynical character in the whole series. A trait that makes him the only character in the whole series whose openly defiant towards Kessler.
Brandt becomes this as time goes on and the war takes its toll on him.
Dirty Communists: The Communist resistance are shown in an extremely negative light. Particularly when they tip off the Gestapo so that they shoot Francois when he discovers Max Brocard is working closely with them.
An early episode of the first series touches on The Holocaust where Curtis attempts to help a Jewish family escape from Brussels.
Brandt also talks about it with Kessler; he is horrified by it. But Kessler tells him to shut up.
First Name Basis: When John Curtis is first introduced, Yvette refers to him as 'Mr. Curtis', later moving onto 'Curtis', and finally just 'John'. Later, Bradley asks to be addressed by his first name, Nick.
Killed Off for Real: At the beginning of series two, Yvette is killed in a bombing raid. Also, Reinhardt in the final episode, as he is executed by a firing squad orchestrated by a revenge hungry Kessler.
Captain Durnford is this in the third and final series as well as being a Reasonable Authority Figure considering that he prevents Monique from having her head shaved by a lynch mob. Kessler is also this but only towards his girlfriend.
The Quisling: The Lifeline crew pretend to be quislings as a cover for their resistance activities.
Shown Their Work: Many of the more fantastic escape plots were based on real attempts used by Allied airmen.
Snark Knight: Reinhardt is this towards Kessler, making him one of the most interesting characters in the series.
Stock Footage: The same footage of a Mosquito fighter plane is reused over the course of the final series.
Suspiciously Small Army: The Occupation forces of Belgium never really amount to more than about fifteen members of a bizarre SS/Wehrmacht unit. Major Brandt is supposed to be in charge of a Luftwaffe police unit, yet never seems to have any Luftwaffe personnel.
Those Wacky Nazis: Subverted considering that most of the Nazi characters are well rounded, even Kessler.
Train Escape: Of a sort. In an episode in series two, a British airman steals a locomotive from a railway yard to escape German search parties.
Unrequited Love Switcheroo: Monique starts off as Albert's mistress hoping he will abandon his wife and leave with her. However the war ends with Albert free to marry Monique, who had grown tired of waiting and leaves with Captain Durnford.
Villainous Cheekbones: Everyone in this show has great cheekbones, villain or not. In particular, Yvette, Curtis, Natalie, and Brandt.
War Is Hell: Many reminders of this throughout the series, The protagonists often fail.
What Happened to the Mouse?: During the evacuation of Brussels, Kessler's military assistant Wullner is seen leaving with him. In the next episode he has disappeared.
Wounded Gazelle Gambit: A tactic played by undercover Germans pretending to be Allied Aircrew. Kessler takes this to the extreme and breaks the arm of one such agent so his cover will look more convincing.