'Don't move yet. I'm going out of the front door. They'll rush me then. That's your chance to go out the back way. Got that?'-'Quite clear.'-'Good! But don't think I'm exaggerating. My chances of getting out of here alive are about one in a hundred. Yours are one in ten. They'll kill you without the slightest compunction if they think you're with me. I don't know what you're doing here, but it doesn't matter. Make for London. If you get there, tell them what happened.'Biggles, Algy and Ginger accidentally arrive in Spain during the civil war. After a chance encounter with a British Intelligence agent who passes them a coded message which has to be got back to the Ministry of Defence in London, they are involved in a desperate chase to get back home with the evil chief of Intelligence and Propaganda after them.