The play starts out with Oswald Alving returning home to visit his mother one of the few times he has visited since leaving home as a young boy. He was sent away to prevent him from becoming morally tainted by his father, Captain Alving, who later died of syphilis. Manders, the mother's former lover, also visits and tells off Mrs. Alving for not living a more conventional life and having an education. In the play, Oswald reveals that he is also suffering from syphilis and will inevitably develop dementia. It is implied that he has gotten syphilis from his father's promiscuous life, and that he is paying for his fathers sins. To make up for the past and to prove her love, Oswald asks his mother to give him a fatal dose of morphine when signs of dementia appear. At the end of the play it is not clear what she will do.
The play raises an interesting issue of corruption. How did Oswald get syphilis from his father? Mrs. Alving is evidently not infected and Oswald had presumably never shown signs of congenital syphilis, although a physician in Paris told Oswald that he had been "worm-eaten since birth." The implication that the syphilis is passed down from his father is bizarre because it is a sexually transmitted disease.
Could Oswald be promiscuous like his father was? Perhaps, but the implication is that the syphilis is a "ghost" of his unusual family and childhood. The play also raises the more contemporary issues of assisted suicide and euthanasia. Will she or won't she agree to give Oswald the morphine? Will the lethal injection be proof of a mother's love? Or just another family sin?