The Doctor explains that the fungus is an alien life form, known as the Hoothi. The Hoothi feed on death and decay, and travel in giant organic spheres filled with toxic gases that are invisible to tracking systems. They are master planners, laying traps for their enemies across time; everyone infected by the spores is now linked to the Hoothi group mind, and they can use them to gather intelligence or do their bidding, before eventually transforming them into fungus creatures. The Heavanites were a race that the Hoothi regularly harvested and used brainwashing to convince that they were gods. The body at the dig is of a woman who rebelled against them and the archway is a telescope she built to spot the approaching spheres. With no way of getting help the Doctor seemingly gives up hope of beating them. Roisa, realising that she is infected, straps explosives to her body and goes to destroy the Church, but she is unable to pull the trigger and Phaedrus leads her to the crypt to meet her new masters. Jan, furious with the Doctor for doing nothing, decides to take action himself. He thinks that, with the help of the telescope, they might be able to attack the sphere in a shuttle with explosives. Although he tries to leave Ace behind, she comes along anyway. Ace, though, leaves a note for the Doctor suggesting that, if she doesn't make it back, he should take Benny as his new companion. Approaching the sphere she asks Jan to marry her and he accepts, but at the last moment everyone except Ace explodes into the fungus — including Jan. In the confusion, Ace falls into an escape pod and falls back to the surface.