Katrina Lyons only visited Cresdon Green for the weekend to see her parents (and, incidentally, ask if they might lend her the deposit for a flat). Unfortunately, this happened to be the weekend when aliens launched an invasion of the village and put a force-field around it. Katrina is trapped in the place where she grew up, under the cosh of alien oppression, living with her parents.
The invasion, led by warlord Uljabaan, is a covert pilot scheme for a full invasion of Earth. Katrina determines to stop it, and sets up a resistance movement. Disappointingly, her sole recruit is sarcastic stoned teenager Lucy Alexander - everyone else is keen not to rock the boat, and some think having the world run by alien marauders might actually be an improvement. But Katrina presses on,

desperate to save the world, and also to get out of here.
This book collects the scripts for the pilot and first series of the BBC Radio sitcom.