The only difference is that they changed the tips on each of the cartridges so they fire bullets made out of exotic Mech-metal, making each shot armor-piercing (which Pope compares to using depleted uranium tipped rounds, but much more powerful). The human resistance does not know why the aliens are using Earth building materials and ammunition, only vaguely speculating that the aliens planned for the invasion to rely on local resources to support itself. Matt remarks that it's not fair that the Mech-metal used in the Skitters' robots gives them such an edge in combat that the humans don't have, which inspires Pope to start experimenting around with the recovered Mech-metal they have. Meanwhile, Dr. Anne Glass decides to perform an autopsy on the corpse of the Skitter she killed, which she hasn't had a chance to perform yet because of the temporary evacuation instigated by the incident with the 7th Mass. All previous attempts to perform autopsies on dead Skitters have been unsuccessful, because their innards rapidly decompose into unrecognizable mush very soon after they die. In the first months of the invasion the humans were just running for their lives and couldn't carry Skitter corpses back from the front lines, and even when they could bring one back later on, they had already decomposed internally. Because the captured Skitter died right inside of their base, it's their first real opportunity to successfully autopsy one. Lourdes assists Anne with the procedure, because as a first year medical student she's the closest thing to a nurse she has. They discover that while the Skitters have tough leathery skin and carapace armor, their internal structure isn't that much different from terrestrial vertebrates, including an endoskeleton, cardio-vascular system, and nervous system. Anne then confirms her fears when she saws through the armored carapace of the Skitter's back, and finds that it has a harness attached to its spine, identical in structure to the ones attached to the human children. The implications to Anne are clear: the Skitters were themselves harnessed, and might not always have been Skitters. Particularly because the harness was found "within" their outer carapace, it seems that they used to be some other kind of lifeform, captured by the tall humanoid aliens who used the harnesses to mutate them into shock-troops. Anne realizes this means that the harnessed children are being slowly mutated, either into Skitters or something like them. While returning to base, the scouting team meets a strange woman (Blair Brown) that invites them into her home.