Sometimes you have to cross boundaries to do justice ... Detective John Rebus has spent his entire professional life putting Edinburgh's criminals behind bars. Now he is in prison himself - and is having a hard time. Because while Rebus' old enemies lie in wait for a small moment of weakness to finish him off, the legendary Scottish commissioner finds it difficult to keep the upper hand. At least until the mysterious murder of a fellow prisoner awakens Rebus' hunting instinct: The crime happened at midnight in a locked cell. And together with a whole series of inmates, various prison guards are also under suspicion. Without an official mandate, without any authority and without a safety net, Rebus must carefully weigh his every step so that he does not become the next victim himself...