Harry Wallis was once the partner in the police force of Marty's father, Larry Hopkirk, until Maurice Crabbe killed Larry and disabled Wallis, in revenge for their killing of his brother, the hardened criminal Sidney Crabbe, though Maurice is also left severely disabled by the incident. Marty's tuition from Wyvern concludes, and he is then able to enter Limbo, but there he realises that its attractions are only superficial. Now that Wallis is approaching the end of his life, to salve his remorse he hires Jeff and Jeannie to locate Maurice Crabbe so that he can give him some of his savings to pay for his care. (thetvdb.com)