The home of the Blackwoods near a Vermont village is a lonely, ominous abode, and Constance, the young mistress of the place, can't go out of the house without being insulted and stoned by the villagers. They have also composed a nasty song about her because Constance is looked upon as the local Lizzie Borden, with double the murders attributed to her. Though she has been acquitted, it is believed that she had done away with four of her relatives by feeding them rat poison. There are two of the relatives left, however, and they share her gloomy seclusion. One is a dotty old uncle, who is confined to a wheelchair. He is writing a book on the case, but he can't remember some of the details. The other is her pretty little sister of fifteen who is fiercely protective toward Constance. There is, in addition, a small black boy living in the house, who looks on the eerie events as a game. Then a youthful cousin arrives from abroad and falls in love with Constance, though there is a suspicion that he is mainly after her money. With the atmosphere of impending doom properly taken care of, the play sets out on the project of unveiling what actually took place that homicidal night in the Blackwood dining room.