The drama opens with an exceedingly effective situation: Anisya, the second wife of an invalid husband, is in love with the vigorous and powerful young labourer Nikíta, and reproaches him jealously because his father wishes him to marry.
Matrónya, Nikíta's mother, is a wonderful study in the evil side of maternity—its colossal egoism and its willingness to sacrifice everything to the welfare of a beloved child. Matrónya condones her son's adultery, because she hopes that it may lead, when the invalid husband is dead, to a good establishment.
The old father—Akím—represents the good genius of the piece: Nikíta has got an innocent girl into trouble and his father wishes him to atone by marrying her; he insists that moral welfare is the only real welfare, and that, in comparison with it, nothing else matters, and the whole terrible course of the play shows how right he is. Akím represents in the drama the one element of real moral beauty, the one light in the "inspissated gloom," and it is characteristic of Tolstoy that he should ascribe this position to the man upon whom society has thrust its filthiest and most repulsive task; Akím, able to find no other honest work, has become a cleaner of cesspools, and has grown so repulsive outwardly that his own wife feels sick when she approaches him. Nor is he a man of intelligence; his habit of continuously repeating his words makes him appear almost half-witted, and his wife terms him "an old mumbler."
The Power of Darkness produces a terrible effect on the nerves, for the gloom is as dreadful as in Macbeth, and it is not relieved by heroic battle or the splendours of a crown; it is to the last degree sordid—the concentrated essence of sin. Yet the chain of moral causation is linked as firmly as in Macbeth, and we are shown, in the same unflinching way, how crime haunts and sears the conscience, and how the worst punishment of sin is that it leads on to ever more and more sin.
The conflict between the evil genius and the good genius—Matrónya and Akím—turns first on the girl whom Akím has seduced, and Matrónya wins, persuading her son to repudiate the unfortunate orphan whom he has so deeply wronged. Also, to hurry matters on, she persuades Anisya to give her husband sleeping-powders which are really poisons.
The second act shows us the working out of this crime: with tragic irony we are made to see that Anisya has no particular objection to poisoning her husband; what she does mind is that he dies so slowly; his horrible sufferings wring her heart, yet she hates him the more for the grief he causes her.
Anisya could not maintain her cruelty were she not continually urged on by Matrónya; she has not even the consolation of Nikíta's support, for Matrónya will not permit him to be told; again with grim tragic irony she declares that he is so kind-hearted that he could not kill a chicken.
In the third act events have moved a stage further. Nikíta and Anisya are married, but further than ever from happiness! Nikíta has learnt of the crime; he regards his wife as a murderess, feels her hateful and repulsive, and, with his usual soft-hearted sensuousness, has turned for consolation to his wife's half-witted stepdaughter—Akoulina. Anisya has to bear all alone the dreadful consciousness of her guilt; she has the bitterness of seeing Nikíta spend on another the money for which she, as she feels, sold her soul; Nikíta beats her, and her passion for him enslaves her so that she can make no real protest. She is surprised herself at her own weakness: "I haven't a grain of courage before him. I go about like a drowned hen."
Anisya's only hope is to get rid of Akoulina by marriage, but the neighbours suspect something and hold aloof. Even Matrónya, always on her son's side, has turned against the unhappy daughter-in-law; the one person who pities her is old Akím, who warns his son that he is acting against God and on the road to ruin.
Again Tolstoy reminds us of Macbeth; his peasant heroine has gained all she desired, but it is hollow and worthless, and she envies her victim in his very grave.