Orgon’s home is a happy one. Orgon is married to Elmire, a woman much younger than he, who adores him. His two children by a former marriage are fond of their stepmother, and she of them. Mariane, the daughter, is engaged to be married to Valère, a very eligible young man, and Damis, the son, is in love with Valère’s sister.
Then Tartuffe comes to live in the household. Tartuffe is a penniless scoundrel whom the trusting Orgon found praying in church. Taken in by his words and his pretended religious fervor, Orgon has invited the hypocrite into his home. As a consequence, the family is soon thrown into chaos. Once established, Tartuffe proceeds to change their normal, happy mode of life to a very strict one. He sets up a rigid Puritan regimen for the family and persuades Orgon to force his daughter to break her engagement to Valère in order to marry Tartuffe. He says that she needs a pious man to lead her in a righteous life.
Valère is determined that Mariane will marry no one but himself, but unfortunately Mariane is too spineless to resist Tartuffe and her father. Confronted by her father’s orders, she remains silent or remonstrates only weakly. As a result, Tartuffe is cordially hated by almost every member of the family, including Dorine, the saucy, outspoken servant, who does everything in her power to break the hold the hypocrite has secured over her master. Dorine hates not only Tartuffe but also his valet, Laurent, for the servant imitates the master in everything. In fact, the only person other than Orgon who likes and approves of Tartuffe is Orgon’s mother, Madame Pernelle, who is the type of Puritan who wishes to withhold from others pleasures in which she herself would not indulge.
Madame Pernelle highly disapproves of Elmire, maintaining that in her love for clothes and amusements Orgon’s wife is setting her family a bad example that Tartuffe is trying to correct. Actually, Elmire is merely full of the joy of living, a fact that her mother-in-law is unable to perceive. Orgon himself is little better. When he is informed that Elmire has fallen ill, his sole concern is for the health of Tartuffe. Tartuffe, however, is in fine health, stout and ruddy-cheeked. For his evening meal, he consumes two partridges, half a leg of mutton, and four flasks of wine. He then retires to his warm and comfortable bed and sleeps soundly until morning.
Tartuffe’s romantic designs are not really on the daughter, Mariane, but on Elmire herself. One day, after Orgon’s wife has recovered from her illness, Tartuffe appears before her. He compliments Elmire on her beauty and even goes so far as to lay his hand on her knee. Damis, Orgon’s son, observes all that goes on between them from the cabinet where he is hidden. Furious, he reveals to his father what he has seen, but Orgon refuses to believe him. The wily Tartuffe has so completely captivated Orgon that Orgon orders his son to apologize to Tartuffe. When Damis refuses, Orgon, violently angry, drives the young man from the house and disowns him. To show his confidence in Tartuffe’s honesty and piety, Orgon signs a deed of trust turning his estate over to Tartuffe’s management and announces his daughter’s betrothal to Tartuffe.
Elmire, embittered by the behavior of this impostor in her house, resolves to unmask him. She persuades Orgon to hide under a cloth-covered table to see and hear for himself the real Tartuffe. Then she entices Tartuffe, disarming him with the assurance that her foolish husband will suspect nothing. Emboldened, Tartuffe pours out his heart to her, leaving no doubt as to his intention of making her his mistress. Disillusioned and outraged when Tartuffe asserts that Orgon is a complete dupe, the husband emerges from his hiding place, denounces the hypocrite, and orders him from the house. Tartuffe defies him, reminding Orgon that according to the deed of trust, the house now belongs to Tartuffe.
Another matter makes Orgon even more uneasy than the possible loss of his property. He had been in possession of a box that was given to him by a friend, Argas, a political criminal now in exile. It contains important state secrets, the revelation of which would mean a charge of treason against Orgon and certain death for his friend. Orgon has foolishly entrusted the box to Tartuffe, and he fears the use the villain might make of its contents. Orgon informs his brother-in-law, Cléante, that he will have nothing further to do with pious men and that, in the future, he will shun them like the plague. Cléante, however, points out that such an extreme reaction is the sign of an unbalanced mind. He says that it is not fair to cast aspersions on religion itself simply because a treacherous vagabond is masquerading as a religious man.
The next day, Tartuffe follows through on his threat, using his legal right to Orgon’s property to force Orgon and his family from their house. Madame Pernelle cannot believe Tartuffe guilty of such villainy, and she reminds her son that, in this world, virtue is often misjudged and persecuted. When the sheriff’s officer arrives with the notice of eviction, however, even she finally believes that Tartuffe is a villain.
The crowning indignity comes when Tartuffe takes to the king the box containing the state secrets and orders are issued for Orgon’s immediate arrest. Fortunately, before the king has a chance to examine the contents of the box, he recognizes Tartuffe as an impostor who has committed crimes in another city. Therefore, because of Orgon’s loyal service in the army, the king annuls the deed that Orgon made turning his property over to Tartuffe and returns the box to Orgon unopened.
Synopsis from: http://www.enotes.com/topics/tartuffe#summary-the-story