Once again, the X-Venture Xplorers find themselves in the past- 430 million years way back when, in the Silurian era! Somehow, Rain managed to snare Emily in one of his schemes to collect ancient treasure. However, they find far more than they bargained for when a group of prehistoric shellfish decide to snack them! Guess you have to expect that sort of thing while you're PUTTERING IN THE PALAEOZOIC!