In the morning, Dexter's just finishing getting dressed when Deb stops by and, without preamble, asks him how he was "so perfectly prepared" to kill Colin Hanks. Dexter tells her he found the plastic wrap in the storeroom (churches have lots of call for it, don't you know), and the knives belonged to Colin Hanks. Neither of those is particularly believable, but when Deb goes on that he wasn't in his work clothes (remember he said he came to do a forensics sweep) and had an apron and plastic sleeves, he at first doesn't even bother to try to explain, merely saying he's sorry he put her in this situation and somewhat condescendingly adding that she looks "stressed." She's like, duh, so then, having had time to invent another alibi, he says that his job can get messy, so he always keeps a change of clothes in the car, and everything else she saw was part of his kit. I have to say, though, as lame as his explanations may sound to us, the viewers, I think it's fair to conclude that if Deb one hundred percent wanted to believe him, she would. But something has changed within her and no matter what words are passing between them, it's clear her trust in him has been broken. I mean, better late than never. After bringing up the "I know what I'm doing" quote, she tells him this whole thing doesn't feel right and he replies with the first honest thing his said in this conversation: "I know it doesn't." They regard each other for a moment, the air thick with mistrust, until he gets up and then turns back to tell her he never meant for her to be involved. She points out that irrespective of his wishes, she is, and he regards her sadly for a moment before saying they need to go to work. He heads into his bedroom...

...whereupon he sits down a bit before entering another flashback in which he enters the house to find Young Deb inconsolable in the arms of their mother, who explains that they had to give the dog back. She apologizes for getting the dog without talking to Harry, saying it's all her fault, but Young Dexter looks a bit heartbroken himself...

...and in the present, DVO admits that everything is his fault. Looking purposeful, he heads back out to Deb and apologizes again, but Deb's phone rings and she gets the news of Anderson having been shot. With a "Jesus fuck," she tries to get Dexter to go with her immediately, but he lingers with a lame excuse about his keys. She clearly doesn't buy it, but neither does she have time to argue, so she bolts, whereupon Dexter heads back into his bedroom, kicks in a hollow section of the wall, and retrieves the bag we saw in the earlier scene. DVO says that he doesn't want to run, but if Deb doesn't let up, it may be his only option. I see now that he's got a couple extra cell phones in there as well, in case it becomes relevant. Dexter gives the photo on his desk of him and Harrison a meaningful look, probably thinking that if things go back to normal, he'll get Deb and Harrison a puppy.