[1] Franz portrayed King Ahab in the 1953 biblical low-budget film Sins of Jezebel, Jethro in Cecil B. DeMille's The Ten Commandments (1956), and Jehoam in Henry Koster's The Story of Ruth (1960).

Dropping his surname, Franz next acted with the Provincetown Players in New York's Greenwich Village, a hothouse of theatrical ferment that had first brought the world the dramatic works of writers Eugene O'Neill, Susan Glaspell, and Edna St. Vincent Millay.

He made his film debut in a bit part, in 1947, in Killer at Large, but followed that brief appearance the next year with a memorable role in the motion picture The Scar (also titled Hollow Triumph).

He played such intellectuals as Dr. Stern in The Thing from Another World (1951), a university professor in The Four Skulls of Jonathan Drake (1959), and Justice Louis Brandeis in The Magnificent Yankee (1950), a role he reprised in the 1965 television adaptation.

Franz performed as well in two separate remakes of Al Jolson's 1927 cinema classic The Jazz Singer, each time playing the key role of the aged and ailing synagogue cantor upset by his son's decision to pursue a secular show-business career rather than continue the family tradition and follow in his father's religious footsteps.

Always dedicated to the theater, despite his television work, Franz in 1961 performed in the world premiere in Los Angeles of Edna St. Vincent Millay's poetic drama Conversation at Midnight, co-starring with James Coburn and Jack Albertson.

Two years later, Franz was cast as psychiatric clinic director Dr. Edward Raymer in 30 episodes of the weekly ABC medical drama Breaking Point with co-star Paul Richards.