Richard is offered early retirement and so ponders over the possibility of having to spend all, day everyday with Hyacinth. Emmett is enraged when Hyacinth ends up rehearsing a performance for the old people at the Church Hall with him (she sings, off key, “You can’t get a man with a gun” from Annie Oakley), and a tranquilised Rose arrives at the scene wanting to become a nun. Rose ends up in the closet with the Vicar, who has gone there to hide from Hyacinth, and the Vicar’s wife arrives and finds them. Rose, who has collapsed on top of the Vicar, tells the Vicar’s wife: “It’s all right. I’m going to be a nun.”
I’ve seen that episode and you’re right it was funny. I’ve probably only seen 10-15 episodes and that happens to be one of them.