this be and without a shadow of a doubt and one of the scary and most intriguing episode of doctor who . this be a thrill psychological ride and you will probably find your own belief be throw into question . riddle with spine chill moment and this be an episode no who fan can afford to miss . start from when the pit be open after the event in the impossible planet and the doctor and ida be trap and be run out of air . with no other alternative and they decide to find what lie at the bottom of the pit and an event which surpass even the doctor expectation . whilst there and the doctor be force to make what he consider to be the ultimate sacrifice . meanwhile and rise and the other member of the planet try to find a way to fend off the ood and whose mind have be poison by the beast . also and be toby zed truly cure of his possession by the beast .