A series of teen suicides becomes the catalyst for something much darker in Samantha Hayes’s What You Left Behind, a murder thriller that begins with the bizarre prologue, the tragic motorcycle accident of a young homeless boy in the village of Radcote, England. DI Lorraine Fisher has just come to Radcote with her teenage daughter Stella to visit her younger sister, Jo. Although she lives in Birmingham, Lorraine loves to occasionally return to her childhood home, where she always seems to be protecting Jo and watching out for her. Jo is just happy to see Lorraine, but she’s also mildly antagonistic and distracted, confessing to her sister that she secretly carried out an affair.

Jo also worries about her teenage son, Freddie, whom she thinks has been cutting himself. She also thinks Freddie is seriously depressed, and she’s clearly exasperated at the notion that he refuses to confide in her his troubles. Indeed, all of Jo’s family--and all of Radcote, for that matter--are in shock after hearing about the lad who recently killed himself. Dean Watts was only nineteen years old when he stole a motorbike and drove it headlong into a tree. There’s also the crazy fact that six kids from the locality have killed themselves within two weeks.

Ever the steadfast police detective, Lorraine is unconvinced that the boys, particularly Dean, really committed suicide. As the web of events shaping the mystery keeps getting tighter, a son’s life hangs in the balance, and a desperate mother is willing to do anything to be reunited with him. Also desperate is Sonia Hawkswell, who works as the New Hope Homeless Center, just a short drive from Radcote. Lorraine notices that Sonia looks extremely thin and her skin is tinged gray. She also has a tangible air of sadness about her, an aura of grief that seems to be gradually consuming her. Jo tells Lorraine that Sean was a regular here at the shelter and that Sonia knew him well. Sean’s sudden death has absolutely guttered Sonia and brought back horrific memories of her son, Simon, who had also committed suicide a few months previously.

It’s hard to imagine the presence of such evil in this bucolic setting. But something is stalking these teenagers, young boys whose bodies were once precious and full of life. Lorraine’s antenna is piqued by Dean’s death even as local DI Greg Burnley--with whom Lorraine is acquainted from a previous case--puts her on notice, clearly fraught with resentment at this upstart newcomer who has no real authority to be investigating anything in the parish. Lorraine is convinced that Burnley had his blinkers on. She also thinks he is having difficulty sticking to the official story of two lads dead from the same homeless shelter. He’s not interested in reopening the Dean Watts case, and clearly he doesn’t believe the witness who says he saw a second person on the motorbike.

Then Freddie goes missing. Jo tells her sister that his backpack is gone as well as some of his belongings. What was Freddie supposed to say? That “a crazy psycho killer” was texting him from a number he didn’t recognize, and that he’d also witnessed another boy, Lenny, being beaten to death? Freddie’s only real friend is Sonia’s daughter, Lana, who also volunteers at New Hope, yet Lana has no idea of Freddie’s whereabouts and is often more concerned with trying to assuage some of the guilt she still feels over her brother’s death.

The pivotal character is the ongoing drama is autistic Gil, who seems to fuel the mysterious activities in the parish. Gil likes to spy on everyone and he also likes to paint, his pictures skewering around the edges of grotesque. Lorraine is convinced that Gil knows more about Dean’s suicide and Simon’s death, and also the secrets Simon’s handsome father, Tony Hawkswell, might be hiding. Gil’s voyeurism is apropos; Lorraine is also a voyeur who peeks into the private life of Jo and her ex-husband and also into the reasons behind Sonia’s unnerving depression. All of the characters are by turns sympathetic and horribly fraught. Although their personalities are each distinct, each has a pervading darkness, a blackness most symbolized by the evening storms and the sheets of low swirling cloud that constantly form a claustrophobic creamy-gray canopy over Radcote.

Although I liked the mystery elements of the novel, much of what transpires is unrealistic: from Freddie neglecting to tell anyone about his torturer, to the mystery of who was on the bike with Dean, to the mysterious photographs that Freddie was trying to steal. Ratcheting up the tension, Hayes's pace is deliberative and slow: Gil at risk, but unable to fully communicate what he sees and hears; Freddie snatched from the clutches of death; the robbery at the homeless shelter; the perpetrator stealing a laptop; the suicide note written by Dean; and Dana, who confides in Lorraine but is probably lying. All is a forbidding reminder that death is nearby and innocent teenagers are at risk. The arrival of Lorraine’s husband, Adam, adds urgency to the proceedings. Both are determined to get the heart of the mystery as they begin to sift through the case files from the six suicides that have occurred in the Wellsebury area.

This is a serviceable thriller that gets better as it goes along. The segments narrated from Gil’s point of view reminded me of the much stronger Elizabeth is Missing. But whereas Emma Healey gets to the heart of a woman suffering from dementia with an eerily seductive rhythm, Hayes doesn't quite achieve the same feat with autistic Gil: the reader remains on the outside looking in, as we do with Lorraine, who ends up coming across as the most sympathetic character in the story.