Hovering above the planet Koblos, the Doctor is surprised by what look like ghosts passing through the TARDIS. He soon learns that he has parked in an illegal time-zone. He is arrested by a Time Warden and put on trial. After being sentenced to two hundred fifty years in prison, the Doctor escapes with help from K9 and uncovers the Time Warden's plot to sell his TARDIS on the black market.