The series highlights the risks that the main characters take to rescue the young airmen whilst under German occupation, protecting their safe houses, and evading investigation. By the end of this series Kessler and Brandt are closing in on Curtis, since their investigation into a murder in France has led them to the name 'Monsieur Maurice', which is Curtis's pseudonym. Brandt and Kessler pay their first visit to the Candide to locate him. Kessler's interest in Curtis poses a significant threat to Lifeline and so it is agreed that Curtis will return to England. Kessler orders a troop encirclement of Brussels, but Curtis manages to escape to Switzerland by posing as bus driver for a local Hitler Youth group that is travelling out of the city on a day trip.