The next month, Larsen chaired a party leadership meeting where it was decided that the communists were to take part in sabotage against the German occupiers. Larsen never got the possibility to be a part of the sabotage work as he was arrested by Danish police on 5 November 1942, and incarcerated at Vestre Fængsel. There he was given over to the Germans who transferred him to the Sachsenhausen concentration camp on 28 August 1943. There he was confined to a solitary cell isolated from the rest of the camp by a high wall with electrified barbed wire.