Brett Battles is the author of a successful series of thrillers about a covert operations “cleaner” named Jonathan Quinn. I like that series very much. Insidious is the second book in a spin-off series about Quinn’s former assistant, Nate (have we ever been told his last name? I can’t recall). Quinn and Nate have kept their distance from one another to an extent since the death of Liz, Nate’s girlfriend and Quinn’s sister. So Nate is operating on his own more often now.

In Insidious, Nate is out jogging in the Hollywood Hills one morning when he spots a backpack discarded beside the path. Investigating, he finds the dead body of a young woman at the bottom of a hill. After helping the police with their investigation, Nate figures that’s that.

But his Thai friend Jar feels differently. Jar is a young woman, a computer genius with autistic traits who has been slowly coming out of her shell and growing closer to Nate. Jar shows a surprising interest in the case. This girl, she discovers, was living under a false identity. She was actually the central character in a sensational police case some years back. She had been kidnapped and held prisoner for months, then had miraculously escaped, though her captors were never identified. Now she has been murdered. For very personal reasons, Jar grows obsessed with discovering who killed her, and making sure they face justice.

What can Nate do but help her? Along the way he will not only learn the shocking motive behind the girl’s kidnapping and murder, but also some painful secrets from Jar’s own past.

I found Insidious totally engaging, and moving in parts. I recommend it highly. Cautions for the sort of things you’d expect.