Commercials. Grey early morning light. The Metallicar chugs into the frame. The boys get out and Dean asks, coffee in hand, why exactly they had to get there at 5:30 in the morning. Is that? Could that be? Setting/storyline continuity? Well, kick me in the pants and call me shitcan! Sam exposits that the video never shows Zach Guzman leaving the apartment, so this double they're looking for must have left out the back. The police wouldn't have looked for this trail, Dean realizes, because they think the killer (Zach Guzman) never left the apartment. Why wouldn't have all this hypothesizing happened BEFORE they got to the crime scene? Was Dean just along for the slackjawed ride or something? Sam pokes around the dumpster while Dean leans against the car, griping about the early hour. Sam basically glances to his right and sees about three gallons of blood smeared on a telephone pole. And just when you thought investigation couldn't get easier, an ambulance comes screeching down the back alley. I half expect the boys to hop onto the back for a ride to the next crime scene that will inevitably crack open this case for them.
Cut to the front of an apartment building (which I'm pretty sure is the same one in which Possibly-Hoofed ManBoy decapitated his uncle [also, it's totally not the same building outside of which Zach Guzman was scouting Ass-Thumper]) where police are rolling out the yellow crime-scene tape. The boys find out from a neighbor that he tried to kill his wife as he is ushered into a police car.
Cut to Sam out back of, presumably, Fancypants's apartment, poking around some more garbage cans. Dean jaunts up to his brother all jaunty, quickly dispatching his own doubts when he tells Sam that Fancypants's story is that he was driving home from a business trip when his wife was attacked and that, furthermore, he saw himself in the house when he got home. Sam narrows his eyes: "Two dark doubles attacking loved ones in the same way." OH LORD. That line is a baby-killer. It kills babies. And possibly kittens. Dean proposes that it's the same thing doing it, causing Sam to respond, "A shape-shifter?" Dean motors through his Monster Hypothesizing -- every-culture-in-the-world blah-diddy-blah -- and Sam answers in Pavlovian kind, listing the types of monsters that fit the bill: "Skinwalkers, werewolves." Jensen Ackles is literally fusing words together in his delivery, so quickly does he want to get this exposition out of the way.