Play Safe

From The Public Domain Movie Database: A young boy is playing in the yard with some toy trains under the watchful eye of his pet dog. A real train rolls by and he runs off to get a closer look. The dog breaks its rope and gives chase after the young boy who has managed to climb aboard the now motionless train. The boy has started the train and is headed towards a collision with another train. The dog saves the boy in the last second before the trains collide.