Dalin and Xiaopang are a pair of young brothers. One day, they take their yellow dog skiing and spot a rabbit. They quickly hop on their sled to chase it. Along the way, Xiaopang discovers the footprints of an old bear, and the brothers decide to search for the bear's den. Unexpectedly, they stumble upon a spy wearing a bearskin. Dalin immediately engages in a struggle with the spy, who sheds the bearskin and flees. Xiaopang shouts loudly, "Catch the bad guy!..." Hearing the commotion, the local militia rush toward the direction of the shouts. Xiaopang continues yelling as he gives chase, catching up to the spy and wrestling with him. Meanwhile, the explosive package the spy had placed on the railway tracks ignites, and a train loaded with machinery and industrial supplies approaches rapidly. Dalin wraps a flashlight with his red scarf and signals the train driver. The train comes to a halt, ensuring the safety of both the train and everyone involved. The spy is captured by the militia.