The Ghost Hunter series centred around Roddy and Tessa Oliver, two ordinary children whose lives are turned upside down when William Povey, a shoeshine boy from Victorian England appears in Roddy's bedroom as a ghost and appeals to him for help. The Ghost Hunter is searching for William in order to obtain 'spectral energy' which is only obtainable from capturing ghosts. At first she seems concerned only to "collect" ghosts, but later her intentions become clear. She wants to use their energy to pass through Time itself and thereby have everlasting life. William's energy is especially high which makes him more attractive to the Ghost Hunter. As Roddy is the only person who can see William at first, Roddy is the only person who can help him escape. In their on-going battles, the two boys and Tessa, Roddy's sister, become firm friends and have many adventures together.