Once Upon a Honeymoon is a 1942 romantic comedy/drama starring Cary Grant, Ginger Rogers, and Walter Slezak, directed by Leo McCarey, and released by RKO Radio Pictures.

[2] In the days leading up to World War II, Katie O'Hara (Ginger Rogers), an American burlesque performer masquerading as American socialite "Katherine Butt-Smith", pronounced byüt-smith, is about to marry Austrian Baron Von Luber (Walter Slezak).

After the German occupation of Czechoslovakia, the Von Lubers travel to Warsaw, where the Baron sells arms to Polish General Borelski (Albert Bassermann).

O'Hara and O'Toole escape to Norway, the Netherlands, Belgium and Paris, all of which sequentially fall to the Germans with the clandestine help of Von Luber.

They meet Gaston Le Blanc (Albert Dekker), an American counterintelligence agent posing as a photographer.

O'Toole goes on the air, but after O'Hara shows up at the studio, he cleverly manages to make it look as if the Baron is trying to overthrow Hitler.