Sol-i and Song-i head to Hanyang with the blueprint for a cannon invented by their father. On the way, they meet Japanese pirates and get captured, but Baek Du-geon appears and defeats the pirates and saves Sol-i and Song-i. Sol-i and Song-i arrive in Hanyang and hand over the blueprint to Hong Cham-pan, and Baek Du-gun and the three insect musketeers cause a commotion. Hong Cham-pan, who was handed the blueprint, works with the snake demon and tries to sell the blueprint to a Japanese spy (Miyamoto). Based on the popular segment 'Drumbeat from the Border' from KBS's Humor No. 1 at the time.