Franz is a supporting antagonist of the 1959 musical The Sound of Music and its 1965 film adaptation. He once served as the loyal butler to the Von Trapp family, but later betrayed them in service for Hans Zeller and the Nazi Party.
He was portrayed by the late Gilchrist Stuart in the film.
Franz first appeared when Maria Rainer arrived to the Von Trapp mansion after being hired as the children's new governess. Letting Maria inside the mansion, Franz calls in for Captain Georg Von Trapp, who introduces himself and the children to Maria.
During dinner, Franz receives a visit from the delivery boy Rolf Gruber, who has come by to deliver a telegram for the Captain. Obliging to Rolf's order to give the telegram to the Captain, Franz informs the Captain's eldest daughter Liesl that Rolf has delivered it (being aware that Liesl and Rolf are in love with each other).
Eventually, the Anschuluss (Austria's annexation into Nazi Germany in 1938) has arrived one month after Von Trapp and Maria are married, and as the Captain's best friend Max Detweiller is preparing the children for the Salzburg Music Festival, Rolf arrived with another telegram, which details an offer for Von Trapp to accept a commission in the Kriegsmarine (the Nazi Navy). As it turns out, unlike the Von Trapp family (along with Max and the housekeeper Frau Schmidt), Franz has accepted the new Nazi order over Austria as he makes the Nazi salute to Rolf, implying that he will hand over the telegram to the Captain when he gets home.
When the Captain comes home with Maria and learns about the commission, Franz introduces Admiral Von Schreiber, who intends to personally escort the Captain to the German Naval base in Bremerhaven for the commission. However, both Von Trapp and Maria cleverly convinced Von Schreiber to wait as they too are participating in the festival, which allowed them to escape with their children after their performance.
It is unknown what happened to Franz following the Von Trapp family's escape to Switzerland.
A key difference between the movie and the play:
In the play, Franz revealed himself as a Nazi supporter when Rolf delivers the Nazi commission to the Von Trapp mansion.
In the film, Franz supposedly maintained his loyalty to the Captain until the Anschuluss, as he is last seen scornfully looking at the family trying to escape before being caught by Zeller and his men, implying that Franz has alerted Zeller of the family's intentions.