Within the opening minute of Dexter, we meet the Trinity Killer. A naked John Lithgow attacks a woman in her home, strips her down and is next seen sitting eerily with her in the bathtub. He's calmly telling her to remain calm, as he slices open an artery in her leg and she bleeds out. Very creepy.
We then see Dexter's new life: he's trying to get Harrison to sleep, only to wake up in the morning with Astor complaining about an iPod, the neighborhood kids being loud and his keys in the freezer. The guy is really tired.
Which causes a problem an hour or so later, as Dexter actually messes up a case in court. He brings the wrong file, is discredited as a witness and a killer name Benny Gonzalez goes free. Quinn is mighty pissed at Dexter for this screw up, as he should be. But it does give Dexter a new victim to target; Gonzalez is going down!
In other office romance news: Quinn meets and flirts with a reporter; while Angel and LaGuerta are carrying on a secret affair. The former apparently broke up with Barbara during the off-season.
Deb is also with Anton. He's got a gig on a cruise ship, so he's rarely actually in town. This gives her time to continue to track down her father's former informants and determine which of them had an affair with him. (We know the answer, of course: it's Dexter's mom, Laura Moser.)
Back to Dexter: he actually falls asleep in his car during his initial stakeout of Gonzalez, as life as a father makes it difficult to find time to kill. When he gets back to work, Frank Lundy is waiting there for him. The FBI agent is now retired, but he's back in Miami because the aforementioned murder in the bathtun reminds him of the one serial killer he could never capture, someone he's named The Trinity Killer because he kills in 3s. Based on evidence Dexter found at the scene, it appears as though Trinity has been killing since at least 1979 (when another murder in the same exact bathtub took place).
Deb runs into Lundy in the office and it's quite awkward. These two used to date, of course. The camera also cuts to another shot of the Trinity Killer naked, in the shower, crying. Again, very creepy.
We close the episode with Dexter finally getting Gonzalez alone in a killing room... only for Rita to call because Harrison needs medicine for an ear infection. This forces Dexter to speed up his ritual and he's yawning heavily as he drives home with Gonzalez's remains in his car. Dexter's eyes close and he crashes. His car flips. The hour concludes with his vehicle lying face down on the side of the road.