Police Comics #19

Plas's first assignment as a G-Man takes him north to the Hadley Lumber Company, which was for sale......but whose lumbermen were turning up dead left and right. Further investigation revealed a boneyard in the forest which was protected by killer trees! The trees were the creation of a mad scientist who'd successfully engineered animals to be plants, and vice versa. Thinking he would die in an ensuing forest fire, Plas revealed his secret identity to the scientist's henchmen, who he later saved and allowed to go free if they would keep his secret.