Captain Jack spots Algy on duty at the bomb site, and Rose assumes that she's meant to distract him. "I've gotten to know Algy quite well since I've been in town," Jack says. "Trust me. You're not his type." Over his shoulder, Captain Jack calls in a flirting tone, "Don't wait up!" The Doctor, seeing Rose's confusion, smiles lightly: "Relax, he's a fifty-first century guy. He's just a bit more flexible when it comes to dancing." Just how? The Doctor adds, "By his time, you lot have spread out across half the galaxy." She refuses to put the pieces together. "So many species..." the Doctor grins, "...so little time...." And Rose is a little wigged. "What, that's what we do when we get out there? That's our mission? We seek new life, and..." The Doctor nods, sniggering: "Dance." Which, whatever. Unchain sex from procreation and it turns into art. Ask the '70s.
Captain Jack hops down onto the rails near where Algy is pacing: "Hey, tiger! How's it hanging?" But when Algy turns around, you can already tell: "Mummy?" Jack -- too big, too much -- won't buy it: "Algy, old sport, it's me. It's me, Captain Jack." His smile fades, as he looks on at Algy's confusion and curiosity: "Captain Jack? Are you my...mummy?" Algy begins to cough and falls to his knees, and then begins to change. I wish we'd seen more about Algy, his pluses and minuses, because I think that Jack's feeling something here -- that it's becoming real, but we can't bear witness to that because all we've seen is him getting his ass slapped and then being mean to a dirty young homeless woman. In front of Captain Jack, Rose, and the Doctor, Algy stops being Algy. The Doctor and Jack order the other soldiers to stay away from Algy, and the Doctor murmurs that the effect has become airborne, and that it's accelerating. "What's keeping us safe?" asks Rose. "Nothing" is the Doctor's reply. So of course the air-raid siren sounds at this point, and Rose remembers that the bomb is due to hit exactly where they are. Captain Jack nods, and somewhere Nancy begins to sing. "Never mind about that," says the Doctor. "If the contaminant's airborne now, there's hours left." For what? "'Til nothing," the Doctor says. "To forever. For the entire human race. And can anyone else hear singing?"