This is book number 1 in the Killer Instinct series.
“Detective Inspector Joona Linna takes on a bizarre murder case when a young Swedish family is found brutally slain in their own home. Questioning the surviving witness is not an option, as the young boy's life hangs by a thread. What Linna needs is a hypnotist. Erik Maria Bark is that man, but the problem is he gave up practicing 10 years ago after a tragic accident. The detective won't take no for an answer, so Erik puts the boy in a trance. What happens next won't just threaten everything Erik has managed to rebuild, it will tear families apart, turn friends into bitter enemies, and rob Erik of Benjamin, his only son. Gritty, fast-paced, and impossible to put down.”
— Paula Longhurst, The King's English, Salt Lake City, UT