Mariane's fiancé, Valère, arrives and explains that he has heard in confidence that Orgon is in dire trouble concerning some secret documents which Tartuffe turned over to the king. Tartuffe, he says, has denounced Orgon as a traitor to the king and, since there is a warrant out for Orgon's arrest, Valère has brought money and a carriage and will help Orgon take refuge in the country.
As they are about to leave, officers, accompanied by Tartuffe, arrive. Tartuffe announces that Orgon is now under arrest and the only journey he is going to take is to prison. When Orgon reminds Tartuffe of his indebtedness, Tartuffe merely replies that his first duty is to serve the king and to do that he would sacrifice anything. Cléante tries to use logic against Tartuffe, but Tartuffe only tells the officers to carry out their duty.
The officers, however, perform their duty by arresting Tartuffe and then explain to the rest of the company that the king, who sees into the hearts of all his subjects, knew that Tartuffe was a hypocrite and a liar. The wise and judicious king could never be deluded by such an imposter. Furthermore, the king has invalidated the deed and has pardoned Orgon for keeping the documents of an exile. The wise king thinks much more of a man's virtues than he does of a man's mistakes; Orgon's past loyalty to the king is rewarded, and his mistakes are now forgiven.
As Orgon is about to say something to Tartuffe, Cléante advises him to forget the poor wretch and turn his attention to better things. Orgon then gives his daughter Mariane to Valère to be his wife.
The arrival of Valère with the news that Tartuffe is closing in thickens the plot and brings everything to a climax. Orgon is suddenly the recipient of a kindness from Valère which he does not deserve in view of the way he has previously treated Valère.
Tartuffe's last chance to be hypocritical occurs when he is faced with his devious ways and he can only respond that his first duty is to his king. In order to serve his king, he would sacrifice anyone. These are almost the same words which Orgon used earlier in the play concerning his newfound religion. Thus, the repetition of these same ideas give a final ironic twist to the situation.
The final scene in the drama has been severely objected to on occasion by critics as being extraneous to the plot. In other words, there is nothing in the earlier parts of the play to indicate that the king will play any role in the play. The ending of a drama should arise out of the parts of the drama which have preceded it and should never be imposed upon the drama in such an artificial manner.
One of the purposes of this ending, however, was to flatter the king, who was Molière's patron. In view of the fact that this particular play was banned several times, it seems necessary that Molière try to offer some type of flattering ending.
The flattery is quite blatant when we realize that the qualities attributed to the king are in direct contrast to those exhibited by Orgon. While Orgon was hasty, domineering, and tyrannical over his family, the king is reported to be judicious and forgiving. And whereas Orgon was completely duped by Tartuffe, the king sees through Tartuffe's hypocrisy immediately. In other words, all of the qualities attributed to the king in the speech by the officer are qualities which were missing in Orgon.