As they approached security, Rose and the Doctor again pulled out their identification. They sent the Doctor's pocket litter through the x-ray machine, and Rose preceded the Doctor through the metal detector. This time, the Doctor didn't set it off, but upon reaching the other side, he was promptly called aside by security to be frisked. The security man began to pat him down.

The Doctor looked exasperatedly at Rose.

The man's hands paused for a second when they rested on opposite sides of the Doctor's chest. The Doctor mouthed "cardiac arrest" at Rose again as the man paused, frowning for a second. He dismissed whatever he was thinking about two pulses a second later, though, and was forced to let the Doctor enter the airport.

"How about I take this escalator and you don't, and we race?" asked Rose as they reached the first escalator, mainly to cheer up the Doctor, who had been walking along gloomily and taciturnly since the events at security.

"All right, fine," said the Doctor. Rose stepped onto the up escalator.

The Doctor glanced at the staircase next to the escalators, promptly rejected it, and instead began to leap up the down escalator three steps at a time, nearly knocking several harmless citizens over. Rose burst out laughing as the Doctor's coat flapped behind him. She was still going faster than the Doctor, even though she wasn't even walking up her escalator.

As the two of them stepped off the escalators, the Doctor several seconds behind Rose, the Doctor proclaimed, "I won!"

"No, you didn't!" exclaimed Rose. "I won, it was obvious!"

"Ah, but you didn't say we were time racing, did you?" said the Doctor smugly. "I say it was a race to see who could sweat the most," he continued as he wiped his damp brow with the back of his hand.

"A physical exertion race?" asked Rose incredulously. "No one does that!"

"We just did."

Rose groaned.

"Look at this!" said the Doctor excitedly. "A horizontal escalator!"

He was pointing at the people-mover in the large airport hallway.

"Can we go on it?" he asked.

"Sure," said Rose, happy with his improved mood. At least, until he promptly sat down on the moving handrail, his long trench coat draped over the opposite side of the rail.

"What? No! Get down, you're not supposed to ride on the handrail!"

The Doctor ignored her. Rebellion seemed to be his new policy. A little girl was staring at him, and he waved jauntily at her as the handrail carried him slowly past the gate at which she was sitting.

When they reached the end of the people mover, the Doctor leapt deftly down from his perch. Rose steered him away from the next people mover and into a random tchotchke shop.

"What are you trying to do, get us arrested?" she hissed at him as she dragged him into the shop.

"Exactly!" exclaimed the Doctor, beaming. "That way, we won't have to take a plane!"

"I am never doing this with you again."

"Ah, I was hoping you'd say that!"

The Doctor paused to look at some tchotchkes while Rose searched for some crisps to snack on. When she returned to the Doctor with a couple of baggies, he was staring at a perpetual motion machine.

"Oh, I should examine this with my sonic screwdriver," said the Doctor pointedly. He dug through his pocket in a horribly exaggerated manner, before moaning, "Oh no! That's right, they made me check it!"

"Are you going to be this annoying the whole flight?"

"Yep."

As Rose and the Doctor sat down in the black plastic seats in front of their gate, the Doctor plopped down and began to stare at the ceiling, twiddling his thumbs. Rose opened her bag of crisps and offered the other one to the Doctor. He ignored her, still staring at the nondescript white ceiling. Not quite sure what to do with the crisps, Rose tentatively put them on the Doctor's chest. He didn't move a muscle.

Rose eventually got up to buy a newspaper or cheap paperback to read. When she got back, the Doctor was exactly as she had left him. The crisps had slowly slid into his lap.

"What're you doing, then?" she asked him.

"I'm finding the slope of an undefined line," he replied.

"That's not possible. That's the whole point, it's undefined."

"M-hmm."

About half an hour later, the Doctor leapt up excitedly.

"That's it, Rose! Thank you, that's brilliant!"

"What did I do?"

"Nothing!"

"Oh, okay. Er . . . the flight's going to leave in twenty minutes. Want to use the bathroom before we leave?"

The Doctor hugged her wordlessly before walking away.

Twenty minutes later, the call for boarding sounded over the intercom.

"No way is he taking that long to use the bathroom," muttered Rose suspiciously. She got up and walked over to the bathrooms.

"Uh, Doctor?" she called hesitantly into the door of the mens' restroom. No response. "You in there?"

She'd seen him go in. There was only one option. Rose squared her shoulders and stepped into the mens' room.

Thankfully, no one was using the urinals or washing their hands. Only one toilet stall - the wheelchair stall - was occupied. Grunting was coming from inside.

"Doctor?" called Rose hesitantly, knocking on the door. The grunting stopped suddenly. It's definitely the Doctor, thought Rose. He's trying to avoid me.

She peered under the stall door, and saw the Doctor's feet, along with a strange contraption made of a plastic knife, some sort of alien glue, a rubber band, a picture frame, nail polish, a broken vinyl record, and what looked like a can of hairspray. The plastic knife had somehow been strengthened by this pocket litter, because it was imbedded in the tile floor.

"You're trying to dig your way out?!"

"I don't know what you're talking about!"

"Right, get out of there. NOW."

"We do not surrender!"

"The plane is boarding, and here I am in a men's restroom arguing with a man who uses alien pocket litter to escape the airport."

"Wow, it's boarding already? I won't have to dig out this way! I can just miss the plane!"

"GET OUT!" Rose yelled as she yanked the door to the toilet stall so hard that the hinges popped off. She yanked the door open, to reveal an utterly unabashed Doctor, bent intently over his work, wearing vintage science goggles over his glasses.

Much to the shock of many of the airport's occupants, Rose emerged a minute later dragging the Doctor out. His plastic knife contraption was imbedded in the floor, digging a tiny trench behind them.

Once they were outside the bathroom, Rose pried the Doctor's hand from his device and then stomped down on the contraption. It broke under her heel.

The Doctor seemed to finally admit defeat. His shoulders hunched over and he morosely pulled off his safety goggles and pocketed them. He followed Rose to the boarding line. Even though they were last, they still reached the passport examiner very quickly.

She glanced at their boarding passes and passports, comparing the names on the passes to the names on their passports.

"Rose Tyler . . . Rose Tyler. Doctor White . . . I'm assuming that your first name is Doctor like it is on the boarding pass, right?"

"Yep. Why?"

"Because your passport must be flawed. It says 'Gandalf' White."

"Oh yeah! That's . . . my middle name. The passport people got it wrong, I know."

The woman shrugged. "All right, you can board."

The Doctor looked crestfallen. "Sure you don't want to pull me aside?"

"Yes, I'm sure. Now get on the plane."