Secret Army - Season 2 Episode 6 Scorpion

Brandt receives a visit from his wife Erika, who asks him to let her and their children come to live with him in Brussels as it is becoming too dangerous to carry on living in Berlin with the increasing British air raids. Brandt tells Erika that his work in Brussels may soon be over, as he has successfully infiltrated Lifeline with an undercover agent. Word of this reaches the Candide, and Albert must face the grim possibility of killing all evaders currently in hiding to preserve the safety of the line. However, Max and Dr. Keldermans have an alternative plan to discover the identity of the infiltrator, but the scheme requires the assistance of Natalie’s uncle, Hans Van Broecken, who hates Albert and will not help Lifeline.