This episode focuses on one of Adam-12's most stalwart supporting players, William Boyett as Sergeant "Mac" MacDonald. While on assignment, Mac knocks down a pedestrian in his squad car. Although Officer Pete Malloy (Martin Milner) testifies that it was an unavoidable accident, Mac is accused of reckless driving by four different eyewitnesses. "Back-Up One L-20" was written by a young Stephen J. Cannell. ~ Hal Erickson, Rovi