Marshman, Jr. was known as the third, often forgotten member of iconic writing team of Billy Wilder and Charles Brackett, the trio that penned the script for 1950 Hollywood drama Sunset Blvd featuring William Holden and Gloria Swanson.

Wilder and Brackett feared their talents were going "stale" and were "stymied by a pivotal turn of plot", so they recruited Marshman, Jr. to help freshen up their script, as he was an influential movie writer for Life magazine at the time.

Their collaboration earned the trio an Academy Award in 1951 for Best Writing, Story and Screenplay.

Marshman, Jr. worked for studios such as Paramount, RKO and 20th Century Fox, contributing to the screenplays for 1953's Taxi and Second Chance, starring Robert Mitchum and Jack Palance.

He later quit his career in Hollywood in favour of advertising, taking on a role at Young & Rubicam.