In Slough House, the backwater for failed spies, memories are stirring, all of them bad. Catherine Standish is buying booze again, Louisa Guy is raking over the ashes of lost love, and new recruit Lech Wicinski, whose sins make him outcast even among the slow horses, is determined to discover who destroyed his career, even if he tears his life apart in the process. With winter taking its grip Jackson Lamb would sooner be left brooding in peace, but even he can't ignore the dried blood on his carpets.

So when the man responsible for killing a slow horse breaks cover at last, Lamb sends his crew out to even the score. This time, they're heading into joe country. And they're not all coming home.