 In the third and last of the Columbia series westerns based on "The Medico" stories of James L. Rubel, Dr. Steven Monroe (Charles Starrett) and his friend "Bones" (Cliff Edwards) set up office in a new town and quickly find themselves involved in a cattle-poisoning epidemic that has a rancher murdered and Monroe being accused of the crime. Steve escapes custody and returns, to prove by microscopic inspection of the fatal bullets, his innocence.