The Man from Morocco.

With the ending of the Spanish Civil War, a dispirited band of volunteers from the International Brigades seeks refuge in France. But on reaching the frontier, the band is disarmed, and all are detained as political prisoners. Then come instructions from Vichy that all fit prisoners are to be sent to Morocco to work on the Sahara railway for the Germans. However, one man manages to escape to London with vital information for the Allies.