In 1950s London, an MI5 outcast stumbles upon a secret that will change the world - if he can stay alive long enough to tell it. A stranger's approach offering highly sensitive information seemed routine to an ex-spy turned policeman. But when a body turns up instead of state secrets, Detective Inspector Herbert Smith finds himself in a race against time to solve the murder. For he is not the only one after the dead man's secret. It seems the CIA, KGB and MI5 are all vying to get to the truth first and some are prepared to kill for it. As the Great Smog descends on London, bringing chaos and death, Herbert finds himself facing one of the greatest evils of the twentieth century. At stake is the biggest prize of all: the key to life itself.