The Doctor presses another button, and a door opens behind them, leading to the eighteenth century: the fireplace from before, walls, floors: "There's something you don't see in your average spaceship. Eighteenth century! French! Nice mantel." The Doctor sonics the fireplace -- not a hologram -- and examines it closely as Mickey and Rose wander around. The Doctor is amazed that it's real -- and double-sided: "There's another room through there." Nearby, on the same wall, is a porthole, through which Rose can see space and the outer edge of the ship. The Doctor crouches, looking through the fire into the opposite room. There's a young girl with blonde hair, in her nightgown, staring back. "Hello!" he says, and she replies in a polite fashion. "What's your name?" Reinette. "Reinette, that's a lovely name. Can you tell me where you are at the moment, Reinette?" She looks at him suspiciously, because she's in her bedroom. "And where's your bedroom? Where do you live, Reinette?" Paris, of course: "Monsieur, what are you doing in my fireplace?" The Doctor stutters: "Just a routine fire check. Can you tell me what year it is?" Of course she can: it's 1727. She is seven years old. "Right, lovely! One of my favorites. August is rubbish, though. Stay indoors." He wraps up quickly and says goodnight, and she bids him a good evening.
The Doctor stands back up, thinking. "You said this was the fifty-first century," says Mickey, and the Doctor points out that he also said it could punch a hole in the universe: "I think we just found the hole. Must be a spatio-temporal hyperlink." Which, he admits, is a word he made up because he didn't want to say "magic door." Which Rose, of course seizes on, with a funny voice: "'Magic door' is France? In 1727?" The Doctor nods and gets down to business, taking off his coat and pointing out that her French was correct for the period. Which has nothing to do with anything, but allows Mickey to ask Excellent Questions that Rose can answer about the TARDIS translation thingy. She is all over him, but not in a girlfriend way exactly -- just like an exuberant, slightly dorky young person with an awesome new toy. Just then, the Doctor hits a sweet spot on the fireplace and it goes rotating, like awesome things often do, taking him to the other side of the wall. Rose yells, but we don't care.
The Doctor is now in Reinette's bedroom, where she lies asleep. There's a ticking clockwork sound in the room as the Doctor stares out at the Paris skyline, where it's snowing. At the sound of horses outside, Reinette's eyes open, and she sits up to look at the Doctor. "It's okay!" he tells her. "Don't scream! It's me, it's the fireplace man. Look!" She's startled, but composed. The Doctor lights a candle with his screwdriver and smiles at her: "We were talking, just a moment ago. I was in your fireplace?" That was weeks ago. Months, even. He's surprised; he knocks on the fireplace and listens carefully: "Must be a loose connection. Need to get a man in." Reinette asks who the Doctor is and why he's there, but he's too busy being scared, all of a sudden. He's staring at a clock on the mantel: "Okay, that's scary..." Reinette cocks a seven-year-old eyebrow at him: "You're scared of a broken clock?" "Just a little tiny bit," he tells her. "'Cause you see, if this clock's broken, and it's the only clock in the room..." -- Like in Versailles, years from now, the clock face is broken -- "...Then what's that?" They listen to the ticking together, and Reinette gets scared. The Doctor moves slowly, carefully, hardly at all. "'Cause you see, that's not a clock. You can tell by the resonance. Too big. Six feet, I'd say. Size of a man." Things get altogether frightening at this point; this episode is perfect. "What is it?" asks the little girl, and the Doctor pokes around the room, speaking faster and faster: "Now, let's think. If you were a thing that ticks and you were hiding in someone's bedroom, first thing you do: break the clock. No one notices the sound of one clock ticking, but two? You might start to wonder if you're really alone."