up into the lava below. Angered at the homeless woman's death, the Doctor tracks down Alison and her boyfriend Joe at their home and breaks in demanding that someone tell him what has been going on. Alison tells the Doctor that three weeks ago, strange noises began coming from underground. She has seen mysterious aliens around town watching her. The townspeople have convinced themselves that they need to stay indoors and make as little noise as possible. The Doctor begins making noise to attract the aliens, who burst up through the floor in a pool of lava. Immune to their shrieking cries, he deflects their noises back at them causing them to explode. The Doctor, Alison, and Joe flee next door where the Doctor explains that the aliens have bodies that can remake themselves. He improvises a large explosion which he believes will disable them and buy time. The explosion destroys the two alien worms and causes the noises from the ground to stop. The Doctor contacts UNIT and explains that he is not interested in getting involved in this problem. He gives them all the information he has on the aliens and tells them that once he retrieves his TARDIS he is leaving. The aliens have begun nesting below ground at a site rich with a special volcanic rock the Doctor believes they have adapted themselves to use. He maps out the area and leads a UNIT team down into some caves to find his TARDIS. After a tense exchange with the UNIT commander, the worm creatures attack and the Doctor separates himself from the group and hitches a ride in a giant underground worm to the main lair of the aliens. There he meets Prime, commander of the Shalka. Prime declares humans inferior and subject to their domination. The Doctor attempts to act inept to extract information from Prime, who sees through the act and calls him out on it. Prime reveals that the Shalka are 2000 strong and will be invading the surface soon. The Doctor attempts another bluff, declaring himself a non-human and therefore uninterested in what happens to the humans. Prime orders Alison executed in hot lava, which forces the Doctor to make a deal to spare her life. He allows the Shalka into the TARDIS and de-activates the Master, who turns out to be an android programmed by the Doctor. The Shalka tell the