<P> In the last episode of the season, "The Getaway", Dexter subdues Mitchell and prepares to kill him in the room where Mitchell had held the kidnapped child . Mitchell believes Dexter was sent by God to kill him, and claims that he had tried several times to stop killing, but found that he could not change his "path". He predicts a similar fate for Dexter: he tells Dexter "It's already over", the same thing he says to his victims before he kills them . Dexter then kills him with a hammer . It is revealed in the final scene of the episode that Mitchell killed Dexter's wife, Rita, in the bathtub of Dexter's house, and that he left Dexter's son Harrison in her blood, mirroring the childhood trauma that put Dexter on the path to becoming a serial killer . </P> <P> Miami Metro detective Joey Quinn suspects Dexter of killing Rita, and he connects the dots as for the identity of Kyle Butler . Anxious to further his investigation, Quinn requests permission from Captain Maria LaGuerta, but she denies his request and orders him to leave Dexter alone . Undeterred, Quinn finds Jonah Mitchell amidst being relocated into witness protection with the rest of his family, and tries to show him a picture of Dexter so that Jonah can confirm whether or not it is "Kyle Butler". However, one of the FBI convoys manages to intercept Quinn's attempt before he succeeds, and so Quinn's query remains unanswered . </P> <P> In the sixth season, Dexter hears news about the Mitchell family, who are now living in Nebraska: Mitchell's wife, Sally, and daughter, Rebecca, have been murdered in the same way as were Mitchell's victims . Dexter deduces that Jonah is the killer, and hunts him down . At first, Jonah claims his father killed them both, but later gets into a fight with Dexter, seemingly wanting to die by Dexter's hand . Confused, Dexter gets Jonah to confess that Rebecca actually committed suicide because their mother kept blaming the children for Mitchell's capture; upon finding her, Jonah flew into a fit of rage and killed his mother, bludgeoning her in the same manner that his father killed his victims . Dexter tells Jonah to forgive himself, and leaves . </P>

Who plays arthur mitchell's daughter in dexter