A French flyer helping the British gets help from a barmaid and a priest in order to escape from German-occupied France.
In Paris radio announces the British are attacking the Germans. Paul Lavallier (Paul Henried) and four English flyers head for Paris. They knock out a German soldier. Paul and Baby (Alan Ladd) run from German soldiers. Herr Funk (Laird Cregar) gets information from the soldier. In a cathedral Paul sees Baby, who is wounded and followed. In the confessional Paul asks the priest Antoine (Thomas Mitchell) for help. Antoine will hide the five in a sewer by a crypt. Paul distracts the shadow so Baby can go in; but now Paul is followed. Paul meets barmaid Joan (Michele Morgan) and escapes by a washroom. He hides in her closet. She talks to Saint Joan as she undresses. She sees Paul and slaps him. Paul gives Joan money and a message for Antoine in Latin to talk to the English spy before he is shot. Joan uses the marked money to buy a new dress. Antoine asks the spy to tell him to whom the five may go; but he mistrusted at first.
Joan lets Paul sleep in her bed while she sits up. Paul says he must go. In the cathedral Paul leaves a note for Antoine and is arrested. Funk questions Paul and gives him a pass; but he knows it is Paul and hopes he will lead him to the others. Antoine tells Paul to go for coffee. Paul tells Joan to slap him so he can leave. Antoine tells Paul he is being followed and suggests using Joan. Paul sends Joan with the message, and she is followed because of the money she spent. Joan gives the letter to schoolteacher Rosay (May Robson). As Gestapo troops arrive, Rosay and Joan leave. Joan comes back to Paul with a wounded hand, and he says he loves her. Rosay gives Paul a sewer map and tells him the plan to take a boat.
Paul tells Joan he is going back to England, but he hopes to marry her later. Joan runs after him to warn him. He calls Rosay, but someone else answers. Paul tells Joan what to do, and she goes to Antoine and the four in the sewer. Antoine recites the 23rd Psalm as Baby dies. Paul goes to a theater and steals a truck but is still followed. In a steam bath he fights the man and shoots him. Joan gets a note from Paul that he can't risk seeing her. Funk calls on Joan and finds the note. To save Paul, Joan says she will help Funk. In the church Joan tells Paul how to escape to his friends. Joan leads Funk through the sewers as the others get away. In jail Antoine prays with Joan before she is shot. In the final scene five planes fly.
This war-time spy thriller reflects the current oppression
by the Germans in France as some French and the English cooperate
in the struggle to overcome the Nazi tyranny. Joan emulates the
courage of her patron saint.