The play is set in the home of an unnamed family during a few nighttime hours, specifically the hours of nine to midnight. The parents, three daughters, a newborn baby, an uncle, and the mother’s father all live in a spacious château, but the action takes place in the sitting room, which most of the characters enter at the outset. As they discuss their concern about the health of the mother and infant, they wait for the father’s sister, a nun, and the doctors to arrive. The sick mother is in a room off to the left, and the baby sleeps in the room to the right.

Initial conversations are concerned with the weather, such as whether it is nice enough to sit outside in the garden or whether it is too damp from the recent rain. The daughters and their father wish to be seated outside since it is no longer raining, but the uncle wishes to remain indoors. The blind grandfather’s preference wins out, indicating his controlling role in the family. He also suggests that any untoward event might occur outside—they cannot predict anything. The other discussion concerns the mother’s health; the father thinks she is improving, but the grandfather disagrees. The grandfather heard the mother’s voice, and this has led him to believe she is still quite ill. The uncle (the father’s brother) tries to smooth things over and create a more relaxed atmosphere. He notes that they must not get themselves into a fuss; this is a peaceful night to relax and laugh amongst family.

The grandfather’s anxiety soon dominates the conversation and the play’s tone. They all have opinions about the mother’s situation, in particular, and about illness in general. The uncle notes that the baby has not made a sound since his life began. He finds this unusual and unnerving. They await the mother’s sister, the grandfather continuing to impress his anxiety upon the rest of the family. Waiting for the sister’s arrival turns into apprehension about who or what might be outside. Looking out into the road for her aunt, Ursula instead says she thinks she sees someone in the garden. Though she cannot place anyone, she notices that the birds (nightingales) have stopped singing. The swans in the pond have become startled, and even the fish are diving. This is an indication that something has disrupted them. 

The grandfather comments on the draft, and the three daughters find they are unable to properly shut the door. They head a scythe being sharpened outside that they attribute to the gardener despite the late night. The conversation moves from person to person as everyone becomes more aware of the eeriness of the evening. Another cause for discussion is the light, which is dimmer than normal despite having been filled that morning; and, after he falls asleep, the grandfather’s declining mental condition.

The father and uncle think he does not listen to reason. They believe that at his age, he should be less worried. The grandfather wakes when the clock strikes ten, and he is convinced that someone is at the door. Ursula assures him this is not the case. The group hears a noise, presumably someone entering the home through the basement. Soon everyone starts to hear noises, and they think it is certainly the sister. However, the maid-servant says she did not arrive but that instead, she had gone to shut the door that was mysteriously left open. The grandfather becomes convinced that someone is in the sitting room with them, not just in the house, but the others disagree. He becomes increasingly...