I read that the U.S. Marshall Clayton follows Dexter and Deb as they go to Saxon's abandoned hospital. For some reason they leave Saxon tied up. Marshall discovers him and he convinces Marshall to untie him. He does and then Saxon kills Clayton. This makes sense, because Deb returns there for some reason. Maybe she was returning to finish off Saxon herself or perhaps just arrest him. But, he attacks her. Still not certain she's dead though.
Also, I heard that Dexter gives Quinn his knives. I have NO idea why. Could Quinn take over Dexter's job at the Miami PD??? That's too crazy. I'm not sure I buy that.