The cause of the darkening of the leading hemisphere of the Saturnian satellite Iapetus has been the subject of debate since it was first observed by Cassini over 300 years ago. Even Arthur C. Clarke's 2001: A space odyssey makes reference to it. In this paper, I make the case for the darkening being the result of material being dumped on the satellite from elsewhere. Specifically, I argue that the dark material is essentially cometary in origin, and came to be deposited on Iapetus following a hypervelocity collision between a comet and the progenitor of what is now called Hyperion.