The Alpine tunnel is closed, so two men ignore their orders and head for the St. Bernard Pass, taking them to Italy . . . Later, they learn that if they had obeyed orders, they would have been ambushed.
Stephen Mitchell and Dan Burke are British agents assigned to keep an eye on a scientist suspected of intentions to defect, but in the obscure way of bureaucracy, they have little in common with one another. In the appalling heat encountered along with their unwary quarry at Lake Maggiore, their differences begin to flare into open hostility.
And then Miriam appears, whether irrelevantly or by design, who can tell? The fact remains that Mitchell had known her in Berlin, where she had wanted his help with a problem of her own. Drawn to her in a way inexplicable even to himself, Mitchell becomes ever more deeply involved in Miriam's dilemma until the idea takes root that there is a way to help. The trouble is, the method entails betraying everything for which he stands . . .