S1E677 : The Sandy Beach with No Footprints

Mouri, Ran, and Conan try surfing for the first time with their surf instructor and her much older husband. The couple soon gets into a heated argument over the safety of surfing with an approaching storm, hinting at a troubled relationship. They find the wife dead on the beach the next morning. The absence of footprints suggest a surfing accident. Conan soon observes clues indicating foul play. Sleeping Kogoro reveals that the husband murdered his wife and carried her body to the beach without leaving footprints by crawling inside a cardboard wheel.