Tuominen remained in Sweden until 1956, when he returned to Finland and published three volumes of bestselling memoirs in 1956–1958. Especially the second volume, Kremlin kellot ("The Bells of Kremlin") had a great impact in Finland, being a critical description and an inside view of the Soviet Union under Stalin, written by a former leading Finnish communist who had met both Lenin and Stalin. Tuominen joined the Social Democratic Party, edited its newspaper Kansan Lehti in Tampere for five years and became a member of parliament for one term (1958–1962).