The London Underground is the oldest subterranean railway in the WORLD, so you can imagine since its creation it's been home many paranormal sightings. Tracks have been built on top of plague pits, 'ghost stations' lay abandoned underground and there's even stories of a bizarre, experimental railway that KILLED the few passengers who managed to ride it. Grab your oyster card and mind the gap, it's time for Rory and Kit to investigate...