Rory tries to offer a sensible suggestion about running away but the Doctor and Amy are running toward the oncoming danger and drag him along. They wind up in a room in one of the towers. Positioned in each of the window alcoves, people have been strapped into metal harnesses. They appear to be sleeping. At this point, some of the almost-people come charging in. Introductions are made, sort of. Amy notices that the new arrivals look just like the people in the harnesses. "What, are you identical twins?" Two more almost-people come in, wearing their acid suits. One of them is a woman; her instantly uptight bearing identifies her as the group's leader. Her name is Cleaves, and though it will be a while before anyone actually identifies her by name, that's what I'm calling her. The Doctor uses his psychic paper to identify himself as a meteorologist, sent to check the place out after the solar wave. Cleaves tells her coworker, Dicken, to check the intruders for bugs. The Doctor figures that this is an army-run factory in the 22nd century. The workers are contractors. The Doctor suaves his way into having a look at the factory's critical systems.

Cleaves leads them into another room where a big white vat of something liquid is bubbling away. Pipes attach the vat to a human-shaped tub. "And there you are," says the Doctor, approaching the edge of the tub. It looks like yogurt. "Meet the government's worst-kept secret," says Cleaves. "The Flesh." She calls it "fully programmable matter" and says it's learning to replicate itself. She exposits that they can program the Flesh to become anything, right down to the clothes and voice. The Doctor muses about the soul, but Cleaves scoffs. "It acts like life, but it still needs to be controlled by us." That's what the harnesses are for. The Cleaves before them is Flesh while the original Cleaves is still lying in the harness in the other room. The Flesh copies are called "gangers," short for doppelgangers. The acid is so dangerous that they kept losing workers. Now the gangers do most of the work. Buzz makes a snarky comment about falling into the acid. Jennifer, the one who's prettier than a computer, assures them that "the nerve endings are automatically cut off." Cleaves tells Jennifer to get back to her harness so her ganger can take over. The Doctor sonics the yogurt. He has some difficulty pulling away. "Strange," he says. "For a moment there, it was like it was scanning me!" So what does he do? Sticks his hand in it. Never touch the goo, people. No good ever comes from touching the goo. The Doctor makes several pained expressions, then pulls away with effort, gasping out, "I understand!" He communed with the yogurt and vice versa. It's alive! He consults with his snow globe just as a jolt rocks the building. The Doctor warns them another solar wave is coming, but Cleaves tells one of the workers to keep pumping the acid.