On 20 May 1937, Larsen arrived to a Moscow marked by fear, anti-Trotskyist propaganda and mass hysteria. Many of his old acquaintances had either disappeared or did not dare to meet him. The negotiations with the Comintern developed into a political trial against Larsen, who had still not been forgiven for his Trotskyist past. Although he defended the Danish party line he was pressured into signing a declaration that the DKP would follow the popular front strategy. He was not allowed to leave Moscow before he convinced the Comintern that he had to go home to look after his wife who was sick with cancer and to tend to his work in parliament.