Three friends head off on holiday to the Soviet Union at the height of the Cold War. To their great surprise, the chief of MI6 asks them to contact a space scientist in Yalta while they are there.

After the recent defections by British agents, notably Kim Philby and George Blake, no Western espionage personnel remain active in Soviet territories. The three young men are a perfect cover as innocent tourists unknown to the Russian KGB.

But are they up to it, without experience or training in espionage? How dangerous are the risks and how will they recognise their contact? And why Yalta, a seaside resort on the Black Sea miles away from Moscow?

However, the chief assures them that the success of their mission is vital to maintaining the prestige of the West, particularly the United States, in its bitter rivalry with the Soviets.

This is their remarkable story.