Flight Lieutenant Peter Romsey, a RAF navigator, is one of Lifeline’s latest customers and London are anxious for his swift return – his technical knowledge of the Oboe navigation system is vitally important. Natalie takes Romsey and other evaders down the line, but Romsey is separated from the others and takes the wrong train, finding himself lost in the French countryside. As Lifeline tries to track him down, Romsey finds unexpected assistance from Hugh and Dorothy Neville, an expatriate English couple. A celebrated author utterly disillusioned with the war, Neville must decide where his true loyalties lie when Romsey turns up on his doorstep.

In the aftermath of the Romsey business, a German newspaper publishes British military secrets. Curtis decides that the traitor must be found and dealt with. He travels to France and retraces Romsey’s steps. Meanwhile, Albert is still suspicious of Curtis and decides that once he is away from Brussels he will reveal his true colours. Monique follows Curtis to France to watch him and finally prove whether he is trustworthy or not, while Curtis’ investigations lead him to the Neville residence.