Orgon immediately asks Tartuffe if what Damis is saying is true. (Remember, the old hypocrite has been watching this whole thing unravel).
Tartuffe tells Orgon that he is, in fact a bad guy, that he's awful, sinful, terrible, the worst person this side of Judas. He tells Orgon to believe what he has just been told, and to kick him to the curb, please. No, really.
Orgon doesn't seem to hear what Tartuffe has said. He screams at Damis and calls him a liar.
Damis can't believe it; he can't believe Tartuffe's little reverse psychology trick has worked. When he goes to reason with Orgon he's cut off.
Tartuffe steps in to defend Damis. He reiterates that he, Tartuffe, is full of it, a liar, a hypocrite, an awful human being.
He turns to Damis, kneels before him, and asks him to accuse him some more; he says that he deserves every last bit of punishment.
Orgon comforts Tartuffe then turns and insults Damis.
Damis tries to talk some sense into him.
Orgon insults his son, asks Tartuffe to stand up, then insults him again.
This cycle repeats itself a few times until Tartuffe finally falls to his knees again and asks Orgon to pardon Damis.
Orgon is, of course, blown away by Tartuffe's kindness. He insults Damis some more, then declares that he'll have Mariane marry Tartuffe this night. He then asks Damis to kneel down and beg Tartuffe for forgiveness.
When Damis refuses to do this, Orgon threatens to beat him, then tells him to scram, for good, and never come back. Oh, and he disinherits him too.