Matti Yrjänä Joensuu (born 1948) was a Finnish writer of crime fiction. He was awarded the State's Literature Prize (1982), Vuoden johtolanka prize (1985, 1994, 2004), and he was nominated for two Finlandias. He received the Martin Beck Award in 1987. He graduated as a police in 1973 and worked as a crime investigator at the Helsinki police station's violence group.
There have been a strange succession of violent deaths at Helsinki tube stations. The police are baffled: nobody has seen anything and the tapes from CCTV show nothing.
Detective Sergeant Timo Harjunpää of the Helsinki Violent Crimes Unit has experienced more than enough of the seamier side of human nature in his career, but the forces of evil have never crossed his path in such an overwhelming fashion. Who is the mysterious old woman handing out religious tracts in Latin or the priest who preaches to commuters? Can they be connected to the killings?