 The story is based on the 1969 novel "Catch Me a Spy" by George Marton and Tibor Méray.It was a co-production between Britain, the United States and France, which was filmed in Bucharest, Romania.It was also part filmed on Loch Awe and Loch Etive, Scotland, where the gunboat scenes were filmed, and featured Kirk Douglas running through a herd of Highland cattle which were owned by David Fellowes.