Gil, Warrick, and Sara pull the CSImobile into the driveway of a gutted house; I'm guessing it's Chez Damon. The three enter the house; Gil and Sara wave flashlights around, the beams cutting clear paths through the dusty air, while Warrick snaps pictures. Gil and Sara bemoan the difficulty of working an arson case, noting that fire may ruin a crime scene, but the firemen don't help. Sara notes that the mattress doesn't look as though it belongs in a living room, and Gil explained that it got there via the practice of overhaul -- firemen removing material from hot spots to prevent the flare-up or spread of a fire. Warrick has been silent this whole time. That's just weak, y'all. Gil and Sara wander into Toby's bedroom, noting the gear laid out. Warrick finally speaks! But he asks a dumb question about whether Toby might have used waterproof matches to start the fire. D'oh. The entire team moves into the master bedroom, where the roof is partially burned off and the walls are blackened with soot. A carpet of debris covers the floor. Gil notes that the fire was contained in the bedroom, but the outside of the doorframe -- the part not in the bedroom -- is severely charred, implying that there was some heat and fire damage. Warrick notes that fire takes the path of least resistance, feeding off the most convenient source of oxygen. There -- he's redeemed himself for his earlier dumb comment. Sara follows up, noting that the location of the char is odd given that the outside door isn't burned. She then notes that there's something stuck to the doorknob, something that fused on their with heat. It might be rubber. Alternately, it might be Damon's cooked flesh. Eeew, I just squicked myself out.
Anyway, the team heads into the main bedroom and after taking another slam at Ecklie's lack of investigative prowess -- yow! -- Warrick notes that Ecklie's report has the fire's point of origin being the bedroom closet. The three investigators troop into the area that used to be the closet and talk about how they detect the point of origin for a fire by looking for a V pattern; the size and intensity of the V-shaped scorch mark indicate how widespread the fire was and how it burned. In the Damon case, the V is narrow, indicating that the fire burned quick and hot. Gil leans down to the point of origin, and notices shards of glass melted into the concrete. Sara asks if the concrete around the glass is discolored from the heat; Gil confirms that this is called "spalling" -- this, then, is the obligatory scene where Jacqueline Zambrano decided to show off the research she did for this episode by having her characters recite it chapter and verse -- and spars with Warrick over whether or not Damon really torched his wife and kid, or if there's a more interesting explanation. It's a little odd: Sara's usually the one who's ready to convict first, ask questions later, not Warrick.