There were quite a few of these medium-budget films made - not quite as propaganda, but serving to bolster the morale in Britain in the depths of WWII. This is one of them. Robert Donat plays a fictional British intelligence officer charged with seeking out and destroying a secret Nazi factory that was developing a lethal nerve-gas deep within enemy territory. He plays his part with style and a little humour, ably supported by Valerie Hobson and Walter Rilla, as he inveigles his way into the brutal Nazi infrastructure and risks life and limb to achieve his goals. It's a great boys own adventure...