A cartoonist partially sketches a scene from a Herman and Katnip comic strip before leaving for a break. When the artist leaves the characters on the page come to life and Katkip begins to chase the mice, who scream for Cousin Herman to save them. Incompletely drawn, Herman uses a fountain pen to finish himself and draws a mousetrap. The two wind up outside the drawing board’s boundaries and use art materials such as erasers, inks and the like as weapons against one another.