His seat in parliament is likely to have saved his life. It is suggested that the Soviet Interior Ministry had planned to arrest Larsen, but general secretary Georgi Dimitrov of the Comintern did not want to arrest a member of a foreign parliament and intervened. Arne Munch-Petersen, who had been part of the negotiations with Larsen, did not have that protection and was arrested on 26 July 1937. After three weeks of torture and interrogations, he confessed to Trotskyist activity and was imprisoned. He died of tuberculosis in 1940 in Butyrka prison.