Slow Horses — Mick Herron

Let us be clear about this much at least: Slough House is not in Slough, nor is it a house...

Slough House is Jackson Lamb's kingdom; a dumping ground for members of the intelligence service who've screwed up: left a secret file on a train, blown a surveillance, or become drunkenly unreliable. They're the service's poor relations -- the slow horses -- and bitterest among them is River Cartwright, whose days are spent transcribing mobile phone conversations.

But when a young man is abducted, and it's threatened that he'll be beheaded live on the Internet, River sees an opportunity to redeem himself. Is the victim whom he first appears to be? And what's the kidnappers' connection with a disgraced journalist? As the clock ticks on the execution, River finds that everyone involved has their own agenda ...

Unless the slow horses can prove they're not as useless as they're thought to be, a young man's death is going to echo around the world.