The TARDIS materializes on the far side of the moon and the time safe alarm goes off. Inside is a diary kept by a Captain Richard Halliwell, describing his mission from Earth to the Moon -- in the year 1878. The TARDIS returns to 1878 where the Doctor meets up with the expeditions and the remains of the massacred team member are discovered. The Doctor must find the alien creature responsible for the murder and solve why there is no record of Victorian space travel.