Visibility : London, 1952. As the fog rolls in, the chase begins . . . A stranger's approach offering highly sensitive information seems 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 seeking to unlock the mystery the dead man took with him to the grave. It seems the CIA, the KGB and M15 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. And at stake is the biggest prize of all: the key to life itself.