She meets the human slave inhabitants of the planet, a generally dispirited bunch, other than the rebellious Arak, who is in hiding. The planet is ruled by the Eight-Legs or giant spiders, and their Queen is the supreme ruler. They govern using guards chosen from among the planet's Two-Leg (human) population and their own phenomenal mental powers, amplified by the blue stones of the planet. The Doctor arrives and meets Arak, who explains that the Metebelians are the descendants of the crew of an Earth space ship, which crashed hundreds of years before. A spider on board found its way to the Blue Mountains where, through the effect of the crystals, its progeny grew larger and cleverer. The Doctor works out that a “negative” stone can absorb and reject the power of the blue crystals. He starts a revolt among the humans, now protected by these stones, but this is not effective. The Doctor explores the Blue Mountains and encounters the Great One, an enormous spider that controls Metebelis and desires power over other domains, too. She craves the crystal, as it will complete a lattice of hundreds of similar crystals on her web and magnify her mental powers immensely. She knows the crystal is still on Earth and sends the Doctor there to get it for her. He flees back to Earth with Sarah, not knowing the Queen spider has now implanted itself in his companion's mind. Tommy has given the crystal to the abbot, K’anpo Rimpoche, who is an elderly Time Lord and the one-time hermit mentor of the Doctor. He now lives in peaceful exile on Earth. He tells the Doctor of Sarah's control, and they work together to expel the Queen Spider. A fight breaks out in the monastery between Lupton’s cronies and Tommy. The Abbot advises the Doctor to take the crystal to the Great One. He suggests that, as the Doctor started this chain of events by removing the crystal in the first place, it is up to him to put it back. He departs in the TARDIS with the crystal. On Metebelis Three, Lupton is killed by the spiders after falling out with the council. When the TARDIS lands, the Doctor heads to the cave of the Great One with the crystal. He warns her of the danger of completing the lattice but she does so, anyway. The forces unleashed are too strong