Between the Acts is a novel set on a typical summer afternoon in June 1939, on a country estate in England called Pointz Hall. It centers on the production of an annual pageant that the villagers hold on a terrace outside the estate.

Mr. Oliver is the elderly owner of the estate, a man who demands respect but who is also becoming a bit doddering in his old age. His sister is Mrs. Swithin, who resides in Pointz Hall during the summer. She is senile, sometimes humorously so, sometimes sadly so, and she has a rich imagination. Where Mr. Oliver prides himself on reason, Mrs. Swithin values fancy and faith. Isa is the daughter-in-law to Mr. Oliver and is married to Giles Oliver. Giles has cheated on her, and their marriage is quite strained.

A great crowd of aristocrats arrives for the pageant, including boisterous, middle-aged Mrs. Manresa and her strange companion, young William Dodge. The pageant, a low-budget affair, is written and directed by Miss La Trobe, who takes the production much more seriously than everyone else.

The pageant is based upon the concept of England, her history and famous figures. A young girl represents young England to start the play. The music stalls and the girl forgets her lines, leading to an ignoble start, but soon the production is under way.

William Dodge and Isa talk briefly, and get along very well, almost as if they were twins. Meanwhile, Giles's mind is across the channel to the World War raging in Europe and soon to hit England's shores. He is angry that a silly pageant is being held instead of more serious preparations for war.

The pageant is a medley of short dramatic productions, singing, and monologues. A villager dressed as Queen Elizabeth appears to usher in the Elizabethan era. In a play-within-a-play, this character is treated to a ribald romantic comedy called "Where There's a Will There's a Way" in which a Lothario-type lover and a crusty aunt scheme to marry the man to a young woman, thus obtaining her dowry.

It is revealed that Giles's lover is Mrs. Manresa, and they have a tryst in the isolated greenhouse. William and Isa also have a connection in the greenhouse, but they refrain from any untoward behavior.

There is a Victorian era in the pageant, another short love-based comedy and singing medley, and then the pageant turns into pandemonium when a series of actors dressed as demons and elves (representing the audience, "ourselves") prance about armed with a mirror to show the audience their own image.

The play ends shortly thereafter. The local Reverend Streatfield is incapable of making sense of what was just put on, as are most of the audience. Streatfield's entreaty for church donations is interrupted as a dozen warplanes zoom overhead in a kind of ominous symbol of the coming of war. The audience slowly leaves, and finally Mr. Oliver and Mrs. Swithin retire, leaving Isa and Giles alone in silence for the very first time. The narrator informs us they will have a large fight, but after that they will reconcile.