Born in Copenhagen, he was the youngest of four children and the only boy. Son of the successful sexologist and Psychiatrist Henry Olsen, he spent his childhood with his family in doctors' official residences at several mental hospitals across Denmark. In his late teens, he played in a couple of pop groups as lead Guitarist. He graduated from high school in Rødovre (1970), and studied Medicine, sociology (passed History of Modern Politics) and film making (exam.art.) until 1978.
After a manager career, he began to write full-time in 1995.
Kvinden i buret was adapted into a Danish film by Zentropa in 2012, titled The Keeper of Lost Causes in English. It was the top box office film in Denmark in 2013. A sequel, a film adaptation of Fasandræberne (The Absent One in English), was released in 2014. Flaskepost fra P (A Conspiracy of Faith in English) came out in 2016, also by Zentropa. All three films star Nikolaj Lie Kaas and Fares Fares.
Spidsrod a theater play in acts – finalist in a major drama competition DramaRama in April 2005. Århus Teater, the Katapult stage. Westfälisches Landestheater . in cooperation with Sabrina Ullrich has created a theater play based on ''Kvinden i Buret''. It premiered in Castrop-Rauxel on 19 October 2013.
