The two of them soon found themselves walking through a dark and mysterious cave. With every step, the darkness became more intense, and soon they could hardly see in front of them. But they pushed on, knowing that they had to reach the end of this treacherous cave in order to find the evil Shaggy. As they continued on, they heard strange noises coming from the depths of the cave that made their skin crawl. Suddenly, they heard a loud voice coming from the darkness. It was the voice of Shaggy, and he was plotting his next evil plan. Sonic and Mario knew that it was up to them to stop him.