Orgon is duped by Tartuffe; he loves him more than he loves his family. He wants to give him his only daughter. Orgon's family hates Tartuffe and wants him gone.
Even after Tartuffe attempts to seduce his wife, Orgon still can't believe the "holy" man is a hypocrite. He disinherits his only son and decrees that Tartuffe will marry Mariane that evening. He also signs his estate over to Tartuffe.
Elmire shows Orgon that Tartuffe is a fraud. Tartuffe attempts to blackmail Orgon, but his plan backfires. He's arrested, Orgon gets his stuff back, and Valère is given permission to marry Mariane.