After his usual night of drinking at the local pub, Hubert Flynn (Pete Postlethwaite) returns home and transforms into a rat.

His wife Conchita (Imelda Staunton) thinks that this change is supposed to be a lesson to Hubert and that the reason he transformed is his own fault.

After hearing the news of a man changing into a rat on the local radio, ghostwriter Phelim Spratt (David Wilmot) convinces Conchita to write a book of the story.

With Hubert nearly dead from exhaustion, Conchita calls the doctor (Geoffrey Palmer) and sends Pius to get Father Geraldo (Niall Toibin) to perform the last rites and an exorcism.

However, Hubert's old flame and neighbour, Daisy (Veronica Duffy) becomes sceptical when she hears him yelling that he needs to use the bathroom and calls for the police to investigate.

He then explains that instead of a book about the family's loyalty, Phelim has been writing about their thoughts of killing Hubert and plans to abandon him at the maggot factory.