John Rebus spent his life as a detective putting Edinburgh's most deadly criminals behind bars. Now, he's joined them...

As new allies and old enemies circle, and the days and nights bleed into each other, even the legendary detective struggles to keep his head.

That is, until a murder at midnight in a locked cell presents a new mystery. They say old habits die hard...

However, this is a case where the prisoners and the guards are all suspects, and everyone has something to hide.

With no badge, no authority and no safety net, Rebus walks a tightrope - with his life on the line.

But how do you find a killer in a place full of them?