The TARDIS arrives in a spaceport on Denossus, but for some reason its
engines continue functioning even after it has materialized. As the Doctor,
Jamie and Zoe explore their surroundings, a young woman named Anna attempts
to destroy the shield generator in the centre of the spaceport, but only
manages to attract the attention of the Vortexians who now rule Denossus.
The Doctor tries to intervene on her behalf, but the Vortexians politely
arrest him and sentence him to five seconds in the speculum -- an ordeal
which normally destroys the victim's mind. Anna's father-in-law, Max,
explains to Jamie and Zoe that the Vortexians sealed off the planet from
the rest of the Universe twenty years ago, and have ruled it ever since;
his son, Anna's husband Luther, was recently placed in the speculum for
attempting to destroy the shield generator. The Doctor, however, survives
the speculum, and recognizes the force within as the Time Vortex -- which
leads him to realize where they really are.
Upon being released by the Vortexians, the Doctor and his friends
set up a trap for them, and catch them in mid-transit when Anna lures them
by trying to destroy the shield generator again. While the Vortexians are
trapped, the Doctor switches off the shield generator's holographic sky-
projection to reveal that the spaceport has in fact been removed from real
space-time altogether and suspended in the Time Vortex. The Vortexians
intend to unite all races in harmony under their rule and had transplanted
Denossus into the Vortex as a test of their abilities. They break free of
the Doctor's trap and attempt to arrest Anna, but Max deliberately shouts
a racial epithet at them, causing them to administer a shock to his nervous
system as punishment. But his aging heart can't stand the shock and he
dies, telling the Doctor he knew what he was doing. The Doctor points out
that the Vortexians have broken their own moral code by killing Max, and
the Vortexians punish themselves by restoring Denossus to its place in
the Universe and departing.
