He met fellow POUM member Eric Arthur Blair, (better known by his pen name, George Orwell), and used to chat with him in the cafes of Barcelona. Krehm was in Barcelona during the May Days street battles when the Comintern-affiliated Unified Socialist Party of Catalonia attempted to eliminate the POUM. In June 1937, after the POUM was outlawed by the Spanish Republic at the instigation of the Communist Party, the house in which Krehm was staying was raided by Spanish secret police and he and his comrades were detained with Krehm under suspicion of being a spy He spent three months in jail and was released after a hunger strike, driven by police to the French border, and expelled from Spain in August 1937, arriving in Halifax at the end of November. Krehm returned to Toronto where he wrote a pamphlet, "Spain: Revolution and Counter-Revolution", and toured Canada and the US giving speeches about his experiences in Spain.