|Country of origin||United Kingdom|
|Original channel||BBC 1 (CBBC)|
|No. of episodes||6|
|Other Seasons||Series 1, 2, 3|
The main action takes place in Roddy and Tessa's village and school where the Ghost Hunter is active. One of the Ghost Hunter's chief abilities is her sense of smell. She can sniff out a ghost effortlessly. But Roddy and Tessa do not know who the Ghost Hunter is. They set about trying to discover this so that they can protect William.
One of their ruses is to put garlic all round Roddy's bedroom, where the ghost is hiding, as the smell is said to keep ghosts and evil away. Eventually, the children realise that the Ghost Hunter is Mrs Croker, but only when she arrives at Roddy's house with her "ghost immobilising vapour" (GIV) with which she tries to freeze William, shrink him and put him in a bottle.
Thanks to Roddy's quick wittedness, William escapes and the police almost arrest Mrs Croker but she escapes. Mrs Croker is also, and always, on the look out for other ghosts and has a whole collection of bottled ghosts that is discovered by Roddy, William and Tessa when the two boys save the girl after she is kidnapped by De Sniff and left tied up and gagged in a secret hideout while Mrs Croker and De Sniff go back to the house to look for William.
When she learns that there is to be an AGM (Annual Ghost Meeting) at Chillwood Castle, she and her side-kick DeSniff set up a powerful plan to bottle dozens of ghosts. Her plan is to use ghost-energy for her own wicked purposes, but the plan fails when she attacks the ghosts during a unique ghost celebration that allows them to assume their human bodies once again. Thanks to Roddy, Tessa and William, Mrs Croker falls from the battlements of Chillwood Castle, and is believed to have been killed. De Sniff escapes.