Dexter discoverd a major secret this week: Lundy misread Trinity's pattern. He actually starts his kill cycle by abducting a 10-year old boy (because that's the age Trinity was when his sister died).
Dexter learns this information soon after he watches Trinity take one from an arcade. He spends most of the hour tracking down little Scott Smith - who Trinity had been creepily trying to play trains with in the bomb shelter of an empty house - and eventually does come across Trinity and his victim just as the former is about to dump his body into a hole filled with fresh paint.
A fight ensues and Dexter actually saves the boy's life, but Trinity escapes. We somehow doubt he and Kyle will be spending much more quality time together.
We also got more information on Trinity and Christine, his daughter, this week. She only sees her dad about twice per year, according to his strict rules, but she's able to convince him to meet her in a parking garage. Once there, she confesses to killing Lundy in order to protect her father's identity. She says she knows all about his killings and actually witnessed the a bathtub murder when she was five.
Trinity goes back to his car, angry as Hell, after saying he'll meet Christine at her apartment later. But when there's a knock on her door at the end of the episode, it's the police. Deb's hunch, combined with the DNA off a toothbrush Quinn submitted to the police, has given them enough evidence to take Christine in.
The hour ends with Dexter comforting a crying Harrison. He's always had a soft spot for children, but now that he's a father, Dexter promises his son that nothing bad will ever happen to him.