The hypnotist

From Eileen Effrat
Author:  Lars Kepler
The hypnotist 
A family has been brutally murdered in a Stockholm suburb. The lone survivor is the teenage son who has sustained multiple stab wounds and is in a state of shock. With no clues to follow,  Detective  Joona Linna enlists the help of a retired hypnotist, Erik Bark. The hypnotism works, but unleashes an unforeseen chain of events. Written by a Swedish husband and wife team, this is an intense  and very disturbing novel that explores psychological and physical abuse, revenge and gang violence.