Yes. Dexter came back home, from killing the Trinity Killer, and found Rita dead in the tub in the same manner that the Trinity Killer kills his bathtub victims. I personally don’t think it was a dream sequence at all. That seems rather lame and Dexter is never lame. (other than Deb. She’s annoying) I think the fact that the Dexter’s son was covered in blood was supposed to be significant, but the Trinity Killer is not aware of Dexter’s past.