From Paris, Wollheim fled to Saarbrücken and later to Switzerland. He was arrested in 1939 and held in a series of labor camps in France (Vierzon, Ruchard, Gurs and Septfonds) until his escape in 1942, after which he and his wife hid in the Pyrénées with the help of a peasant woman. At war's end in 1945 he returned to France.