sobakin is at the tsar's palace. he is proud because his daughter is now the tsarevna (the tsar’s wife) and he himself has been made a boyar. but he is also worried because marfa has become very ill. griaznoy comes in and greets sobakin (who are now both boyars). he says that the person who poisoned marfa has confessed. marfa rushes in and tells griaznoi to speak. he says that lykov was tortured and then confessed to having poisoned marfa. lykov was then executed by griaznoi himself. marfa goes mad when she hears this. in her madness she thinks griaznoy is lykov. this eventually makes griaznoy confess that he himself at put the potion into her drink. he did not realize it was poisonous. lyubasha then confesses that she had put her potion in the place of griaznoi’s potion. she blames griaznoy and invites him to kill her. he kills her, then he is taken to prison to be executed. as he is taken away, marfa, in her madness, once again mistakes griaznoy for lykov. she invites him to return the next day to visit her. then she dies.