In the 17th century, an old Tibetan friend of the Doctor's reached out and touched the mind of an alien disembodied energy, giving it a conduit to Earth. 300 years later, the Doctor returns to the Himalayas to return the Holy Ganta, an ancient relic he was given many centuries ago by the grateful monks at Det-Sen Monastery. On arriving however, the Doctor is treated as a villain–blamed for a series of brutal murders in the area. Jamie and Victoria meanwhile discover the true culprits –the previously peaceful Yeti that live in seclusion on the mountainside have apparently turned violent. The Doctor must convince the monks that not only is he not their enemy, but the real foe – and the power controlling the Yeti –is living amongst them. Their ancient Master, Padmasambhava, is being controlled by an alien entity known only as the Great Intelligence.