The fifth doctor has just left tegain when he is greeted by a fellow time lord in his tardis who tells him that the black guardian is looking for him again. Sadly the doctor reinstalls the randomizer. Meanwhile on earth Martha Jones finds a time disturbance in her garage and when it goes of she disappears. Back on the tardis the doctor has just left a gas giant when he lands on cavas 7 a criminal underworld that has a weak sun so its always dark. He sees Martha being chased by a group of judoon because they think she killed there employer dax jag. The doctor helps her hide and then the two starts investigating to find out who really did it. They find that daxs wound was caused by a x-1.5 beam energy only emitted by the judoons leader unique weapon. They show this to the judoon and in combination with a witness it is enough to convict the judoons leader. The other judoon throw him in jail and then let Martha leave with the doctor. The time lord appears again and tells them that the black guardian was a false alarm. However the doctor cannot remove the randomizer from the tardis and Martha decides to become his companion.