This is the second book by Mo Hayder about Detective Inspector Jack Caffery. I think an early warning is due that, if you have not read 'Birdman,' you need to do so before opening 'The Treatment.' The stories overlap themes and characters extensively. This isn't a bad thing, and if you don't like 'Birdman', you will definitely not like 'The Treatment' one bit. The reverse, of course, is equally true.
Caffery is in the midst of a troubled relationship with Rebecca Morant, the artist he rescued in 'Birdman' and still deeply haunted by the memory of his brother Ewan, who disappeared some 20 years before. Jack knows who kidnapped Ewan, but has never been able to find enough proof. To this day Caffery has no idea if Ewan is alive or dead.
The horror starts with the discovery of the Peach family, has been held captive in their house and their son molested. When the police arrive at the scene the pedophile has made his escape, with Rory Peach in hand. He seems to vanish in the night. The hopeless hunt for Rory brings up all of Caffery's feelings about Ewan. Driven by his own guilt he is always in danger of taking one step too far.
Caffery comes to believe that another family is being victimized even though the police believe they have a suspect. This puts him at odds with Rebecca and with Chief Inspector Daniella Souness. However, he is determined to follow every path, discovering not only a web of pedophiles but clues to Ewan's disappearance as well. This story does not let up to the very end, with every turn something new and grim turns up.
Hayder's characters are spectacular. She manages to let you into the heads of many without ever disturbing the narrative viewpoint enough to lose focus. Plot, action, setting and character, the vital ingredients are all there. Be warned that this is rough ride - take my advice and don't start it at night.