In January 1943, the escape line was infiltrated and betrayed by French turncoat Roger le Neveu, an associate of Harold Cole; Guérisse was arrested in Toulouse in March. En route to prison he managed to get one of the younger members, Fabien de Cortes, to escape and warn the British. After his arrest the line was taken over by Marie Dissard. Guérisse told nothing to the Gestapo interrogators when he was tortured and then was sent to a series of concentration camps, including Mauthausen. No one, neither in the network, nor the French police nor the Gestapo, ever knew O'Leary's true identity.