This article explores the interpreter's agency in wartime. It presents a case study of Gottlieb Fuchs, a Swiss citizen who worked as the interpreter for Klaus Barbie, the Gestapo commander of German-occupied Lyon, during the Second World War. The study focuses on the analysis of his memoirs as a personal narrative and some letters written by former Gestapo prisoners and camp inmates. Gottlieb Fuchs's story is an unusual one: working as a triple agent from 1942 to 1944 in the context of the Second World War, Fuchs collaborated simultaneously with the Germans, the French Resistance and the government of his native Switzerland. Despite their official neutrality in the war, the Swiss used Fuchs as a source of information with which to help prepare for a mobilisation if faced with a German invasion. Driven by solid ideological values, Fuchs used his position to protect political prisoners, and played, therefore, a humanitarian role during the German occupation of France. I focus on this particular case study in order to analyse the role of emotions and ideology in the interpreter's agency in contemporary wars. I argue that emotions have an important impact on the interpreter's agency in extreme conditions. I also posit that the interpreter may not always be aware of the direct or indirect implications of using or misusing his complex positionality to attain certain goals, and that there are unforeseen repercussions that stem from the interpreter's decisions and are beyond his control.