Mrs Fuddle is a spiteful, recently widowed crone who lives alone with her servants and a grandson she despises. When she learns that she has only nine months left to live, she is advised by the doctor to gather family about her to prepare for her impending death. Her gormless prat of a grandson Guy, eager to win her approval and see his family reunited, sets out on a quest to find his four beloved sisters who were sent away mysteriously twenty years ago. At his Grandma's bidding, he vows to bring them all home again in exactly nine months.
Guy Fuddle's search for his long-lost sister Cassandra takes him to America, where she has forged a successful career as a Hollywood big-wig. Guy sets about coaxing Cassie to leave behind the glamorous life of a TV soap star and return to Fuddlewich, her humble childhood home in England. He gets a taste of the good life himself when he lands a job as a garage attendant to the stars.
The search for the second of his missing siblings finds Guy in the French countryside, where he encounters his doe-eyed sister Madeleine studying under France's premier poet, thinker, and pervert Dalcroix. Dalcroix is bent on seducing his beautiful pupil if it's the last thing he does, but her naïve failure to perceive his advances has brought him to his knees. Meanwhile, the overzealous village priest, jealous of the poet's lascivious lifestyle, is plotting to rid the community of him.
Guy finds his eldest and thickest sister Joyce residing in a nunnery, living a perpetual childhood to the chagrin of the Mother Superior. Joyce insists that the Virgin Mary came to her as a tree when she was a child and dropped a conker on her to tell her to become a nun, and she appears never to have fully recovered from the blow to the head. Guy must convince her to leave the sisterhood and return to her biological sisters, but he soon learns that nothing short of a miracle will persuade her to abandon her pious pursuits.
Guy must spring his youngest sister, Roxanne, from a top security women's prison, where she is serving a 50-year sentence for jeopardizing a judge's career by being raped by him. Everyone knows there's only one way out for the prisoners of Long Mangle, and that's to be carried out in a box. But Guy is determined to free his little sister, and he doesn't care if it means having a sex-change operation and getting convicted himself, or even buying a box.
Nine months have passed, and the fated day for the girls' return to Fuddlewich has arrived. Guy is beside himself with joy awaiting the moment when he can at last be part of the big, happy family he dreamt of during his lonely childhood. However, he and his sisters soon learn that it's not their love Granny is after. When Grandma Fuddle's sinister motive for the reunion comes to light and the true reason the girls were orphaned twenty years earlier is finally revealed, the girls join forces to exact their revenge, and Grandma may find herself condemned to a fate worse than death.