January 1947: the coldest winter in living memory. Harry Tennant has been recruited by SIS but is bored by the routine task he has been allotted of retrieving information from war-damaged files. So when he is asked to shadow Joseph Wolff, an Oxford academic, to the Suffolk coast he readily accepts the assignment. But Harry watches Wolff commit suicide and, unable to stop him, he then finds that no one at SIS is either surprised or curious as to why the man has killed himself. Back in London he is switched to a department investigating Zionist terrorism yet finds himself unable to forget Wolff. As Harry makes his own enquiries he begins to discover links between Wolff and a military operation the government would prefer to keep secret, links that - to his cost - lead back to the heart of SIS.