
From the plot overview on Wiki:
'During the action of the play she discovers that her son Oswald (whom she had sent away so that he would not be corrupted by his father) is suffering from inherited syphilis, and (worse) has fallen in love with Regina Engstrand, Mrs. Alving's maid, who is revealed to be an illegitimate daughter of Captain Alving, and thereby Oswald's own half-sister.
The play concludes with Mrs. Alving having to decide whether or not to euthanize her son Oswald in accordance with his wishes. Her choice is left unknown.'
Like Eastenders without the happy ending.
en.wikipedia.org/wiki/Ghosts_%28play%29