The Lost Boy

STORYLINE

A tearful couple appear on television to appeal for the return of their lost son, Ashley. According to Mr. Smith's analysis of the boys' DNA, 'Ashley' and Luke are the same person and, after Chriisie Jackson has called the police, a reluctant Luke is returned 'home'. He is locked in his room by the couple, who are, in fact Slitheen, as is another boy, a child genius called Nathan, though Luke knew him previously as Carl. The Slitheen get in touch with 'the Xylok', for instructions, but the Xylok turns out to be Mr. Smith, who has turned rogue and plans to destroy the Earth by releasing others of the Xylok race.

Luke eventually escapes from the Slitheen but the bigger problem is Mr. Smith, who is trying to kill Sarah Jane and her neighbours. However, help comes from an unexpected quarter, K9, Doctor Who's old robot dog, who now lives with Sarah Jane,and who keeps Mr. Smith busy in combat while Alan prepares the virus that eventually shuts down Mr. Smith and returns him to being Sarah Jane's benevolent helper, whilst the Slitheen escape empty-handed.