Petros was awaiting execution in a Central European death cell. There was only one way out. He could buy his freedom by assassinating the President of the neighbouring state. And to ensure his good faith. he was injected with a fatal drug that would kill him inside four months... Unless he completed his mission and came back to his jailers for the antidote.
Used availability for James Anderson's Assassin
January 1970 : USA Hardback
September 1969 : UK Hardback
June 1971 : UK Paperback