To those who don't really know her, Kate Henderson's life must seem exceedingly ordinary. Civil servant, wife, parent of two teenagers, daughter of an Alzheimer's-stricken mother ... But she's also a senior MI6 officer, and right now she is nursing the political equivalent of a nuclear bomb. Kate's mission to bug an oligarch's super-yacht in Istanbul has yielded the startling intelligence that the British Prime Minister has prostate cancer - and that one of the leading candidates to replace him may be a Russian agent of influence. Is this `intelligence' reliable - or is it an attempt to create chaos within the British hierarchy? Kate's bosses have their doubts. But when the PM suddenly announces his resignation, the hunt for the spy begins in earnest. It's a nightmarish task, made infinitely worse by the revelation that there may be another mole - codename Viper - at the heart of the Establishment. As the tension mounts, an operation that looked as if it might cost Kate her sanity appears poised to do much, much more than that ...