Holmes and Watson are on their way back to Baker Street from a freshly wrapped-up case when they hear shrieking from around the corner, and naturally they charge around the corner to see what's happening. What's happening turns out to be a giant snake with a mirror for a face. They get the woman it has cornered out of the way, and Watson goes for his revolver, but before he can bring the snake down it gets its face over both of them and they're somewhere else.