British intelligence is in a state of panic. Cracks are appearing, or so a run of disciplinary cases would suggest. To cap it all, Willa Karlsson, a retired MI5 officer collapses, the victim of what looks like a Russian poisoning. Leonard Flood is ordered to investigate – and quickly. Notorious for his sharp elbows and blunt manner, Leonard's only objective is to get the job done, whatever the cost. When Leonard discovers that he is also a suspect in the investigation and that Willa's story is less a story of betrayal than one of friendship and a deep sense of duty, he must decide whether to hand her to her masters or to help her to escape.