Charlie Quick (Clive Dunn) is the caretaker at Parkview Rehearsal Hall, where rehearsals are taking place for a production of The Scarlet Pimpernel. But when a member of the cast doesn't turn up, Charlie offers to help.
After complaints about his cooking, Grandad tries to get a vending machine for the hall. However, cooking is not his only problem - Mr. Thorn-Tree is due to visit, a man whose acting career Grandad had accidentally ruined 40 years earlier.
Young Dennis has an audition in France for a roller skating TV show, but doesn't have a chaperone. Grandad volunteers to accompany him, but unwittingly gets involved in a diamond necklace smuggling operation.
Demanding, prima donna actress Amelia Wilcox is coming to the hall to rehearse. There's only two women in the world Grandad cannot stand - and Amelia Wilcox is both of them.
Grandad plans to ask for a pay rise. Unfortunately when Mr. Watkins arrives from the council, he's accidentally reminded of Grandad's age, and that he's overdue for retirement.
Grandad is suffering from insomnia, so stage act The Great Mesmo hypnotises him to fall asleep whenever he hears the sound of a bell. Unfortunately for Grandad, Mesmo forgets to cancel his hypnotic command the following day.
Mr. Watkins decides to take a secret holiday to avoid any more stress after arguing with Grandad. But when the short-sighted Jill visits from the council, she sees Grandad jokingly strangling a dummy - and thinks he's committing murder.
Mr. Watkins finds that there's a £57 discrepancy on the year's accounts, so gives Grandad an ultimatum - either he sorts out the accounts or he will be fired. Grandad plans a way to get out of trouble by pretending he's lost his memory.
Grandad has collected £100 for the social club party by doing odd jobs, but when Mr. Watkins finds out about it, he insists the money belongs to the council. Bert comes up with a plan to fake a robbery in order to help Grandad keep it.
Grandad offers to help Mr. Watkins by judging a beauty contest at the hall. Unfortunately for Grandad, when word gets around that he'll be deciding the winner, his day becomes a series of threats and bribes from involved parties.
Councillor Teasedale gets Grandad and Bert to help him organise a surprise party for Mr. Watkins' 25th anniversary with the council. But Mr. Watkins is paranoid that they're plotting a whispering campaign against him.
The magician Marvello is coming to the hall to perform a magic show, and Grandad and Bert have been assigned to help advertise it. Unfortunately for all concerned, the billboard posters are ruined and Marvello breaks his leg.
Grandad and Bert have won a trip to the seaside, but are prevented from going by Mr. Watkins, who insists the council need to cut back on expenses. Grandad and Bert sneak away to the beach anyway - but unfortunately, so does Mr. Watkins.
Mrs. Tomkins can't afford to put on her play after overspending on costumes. Grandad agrees to talk Mr. Watkins into letting her hire the hall for free, providing she gives him the lead role - but Mr. Watkins also wants the star part.
Mr. Watkins enters the election for Borough Councillor, and tells Grandad he'll knock the hall down if he wins. Determined to save his home, Grandad enters the election himself.
Grandad is told he's due to inherit £250,000 from his recently-deceased cousin. Hearing the news, Mr. Watkins and Amelia Wilcox get together to try to exploit Grandad's new-found wealth.
Grandad and Bert try to repair a blocked water pipe at the hall, and in so doing, discover what Bert believes are ancient Roman artefacts.
Grandad has mistakenly triple-booked the hall, and all concerned demand that their booking should take priority: Mr. Watkins with his ornithology lecture, Mrs. Travers with her costume tests and Amelia Wilcox with rehearsals for her play.
With the hall roof leaking, Grandad takes up a temporary position as caretaker of the council office building. Unfortunately for Grandad, on the way to his new workplace, he causes a traffic accident - with the new mayor.
Bert sees an advert in the paper for a new caretaker at the Transport Research Institute. Looking for a better-paid job and fancying himself as an inventor, Grandad sets to work on his new creations - including wine-powered rocket fuel.
Bert and Grandad try to earn some extra money by moonlighting as waiters, but two of their first customers are Mr. Watkins and his secretary.
Grandad is worried about the health of Captain, his pet parrot. However, through a series of misunderstandings, Mr. Watkins mistakes the vet's advice for a doctor's advice about Grandad.
When things start to go missing from the rehearsal hall, Grandad is implicated and the police are called. Yet when Sergeant Stone arrives to take down the details, Grandad wants to conduct his own investigation.