George Brown attends the funeral for Mercy, his nineteen year old daughter who died of consumption. The ceremony is continually interrupted by the coughing fits of George’s son, Edwin, but soon the gathering breaks up, leaving George alone at the grave of his daughter. His privacy is interrupted when a young man named Thomas Everett arrives to lay flowers on the grave. Furious George sends the boy away, despite Thomas’ protestations that he loved Mercy. It is then that Mercy appears before her father. He is overjoyed at first, but gradually realizes she is nothing more than an apparition created by his own conscience. Nevertheless, Mercy begs her father to forgive Thomas, until the two of them are interrupted by the town doctor. Doctor Metcalf cannot see Mercy and implores George to return home.
George relives a fond memory of Mercy, when he taught her the story of Oedipus and Antigone. The young Mercy appreciates the loyalty between a father and a daughter, but does not understand why such terrible things befell Oedipus. George explains that it was merely fate because “that’s the way the gods wanted it.” The happy memories fade back into the present where George is forced to deal with the fact that Edwin is also dying of consumption. He refuses to allow Doctor Metcalf to tell his son the truth.
Memories begin to interweave with George’s present as he lies to Edwin about his health. At the same time, he relives the lies he told Mercy about the ending of the Oedipus story, her mother’s failing health, and Thomas Everett, the young boy who fell in love with Mercy over their mutual love of ghoulish stories. Meanwhile, the town is stirring with unrest. Edwin is the fourth case of consumption in the family and, according to the dogma of the age, that means that one of the family members is an undead fiend, a vampire, drawing the health away from the Brown household.
Thomas visits the grave of Mercy to find that Doctor Metcalf is investigating the possibility of a vampire in the family. Steadfastly loyal, Thomas refuses to allow any desecration of Mercy’s grave. He goes to warn George, but is greeted only by Edwin. He expresses his sympathies to Edwin over his consumption. Edwin is shocked, feeling very betrayed by his father. George returns and catches sight of Thomas in the house, flying into a rage. He ends up striking the boy. Edwin breaks up the fight and Thomas departs. Edwin confronts his father, asking how he could lie to him. George is unable to answer.
More memories of death and destruction flood George’s guilt as he remembers Mercy’s final attempts to break free of the family by eloping with Thomas while Olive, his older daughter, falls victim to the disease which claimed his wife. Edwin again confronts his father about the lies. George insists he was acting for the best. Edwin replies that George was acting for his own comfort, not his son’s. Angrily, Edwin points out George’s complete inability to let go of anything or anyone. After reliving Mercy’s brutal death, George painfully admits his sins to Mercy’s apparition, expressing his unspoken sense of culpability. Mercy retells him the story of Oedipus. Misfortune befell George the same way it befell the mythological king, not because of anything he did, but simply because of fate and chance.
George returns to his daughter’s grave to find the villagers gathered behind Doctor Metcalf, determined to raise the fiend that is plaguing the family and may soon be plaguing the town. Only Thomas stands between Mercy and their irrational fears. George joins forces with Thomas and together, they repel the superstitious mob. Although they acknowledge that this won’t be the end of the hysteria, they are reconciled in their mutual love of Mercy and agree to stand guard together. With this forgiveness, Mercy’s apparition is freed and departs.