Whilst walking through the woodland of an unnamed world, the Fourth Doctor predictably speeds ahead, entering a cave. Sarah is left to moan about how he always does this sort of thing to her. Mid-whinge, she feels the ground rumbling beneath her. Soon, she is facing a particularly nasty-looking jannosaur. She watches in horror as the giant, slug-like creature begins suctioning up everything in its path. The Doctor appears from the cave in the nick of time to save her from the jannosaur's voracious appetite.