When Arthur Abdel Simpson first spots Harper in the Athens airport, he recognizes him as a tourist unfamiliar with city and in need of a private driver. In other words, the perfect mark for Simpson's brand of entrepreneurship. But Harper proves to be more the spider than the fly when he catches Simpson rifling his wallet for traveller's checks. Soon Simpson finds himself blackmailed into driving a suspicious car across the Turkish border. Then, when he is caught again, this time by the police, he faces a choice: cooperate with the Turks and spy on his erstwhile colleagues or end up in one of Turkey's notorious prisons. The authorities suspect an attempted coup, but Harper and his gang of international jewel thieves have planned something both less sinister and much, much more audacious. The Light of Day was the basis for Jules Dassin's classic film, Topkapi.