When a retired senior member of the Security Service, Clive McTaggart, is found dead in his home, it's put down to suicide. The man had been suffering from cancer so suicide is not an unreasonable conclusion. It's not that simple however. McTaggart had written a book and had arranged for journalist Gary Hicks to visit him that day and Hicks actually saw him being killed. He's soon in touch with Ruth Evershed and MI-5 begins an immediate investigation. Without knowing who might be out to stop the publication of McRaggart's book - and realizing it could even be another part of their own organization or another intelligence agency - they play their cards very carefully. The team get unexpected help from an aspiring journalist, Jo Portman. They also happen to be looking for new recruits.