A prolific screenwriter, Plympton collaborated in almost 300 films. His earliest known credits date back to 1912 as he concentrated almost exclusively on westerns. During the sound era he switched his focus to serials mostly for Columbia, Republic and Universal studios, co-scripting and adapting such chapter plays as Tarzan the Fearless (1933), Flash Gordon (1936), The Spider's Web (1938), The Phantom Creeps (1939), The Green Hornet (1940), Flash Gordon Conquers the Universe (1940), The Masked Marvel (1943), Chick Carter, Detective (1946), Brick Bradford (1947), Superman (1948), Batman and Robin (1949), and Atom Man vs. Superman (1950). Active until 1957, he additionally was one of the principal writers on Columbia's Durango Kid and Jungle Jim series.
Plympton passed away in Bakersfield, California, at the age of 82.