"If I could just reach you, I would kill you!"
Clinging to the side of the speeding boxcar, Donna didn't dare move. She had twined both arms around the rail that ran up the side of the ladder, and all she could do was sneer at the man sprawled across its roof.
"Aw, come on, Donna! Did you see that?" With a toothy grin, the Doctor loosed one arm from his hold on the corrugation on the roof and gestured expansively at the world around them. "It's the wild west! Cowboys and horses and cattle and locomotives! Sheriffs and schoolmarms and frontier spirit! Brilliant!" His breathy exclamations were ripped from his lips by the wind.
"And aliens! Don't forget the aliens!" she shot back. At least the constant rush of air kept her hair streaming out behind her, leaving her mouth free and clear.
"Well..." he drawled, his eyes rolling skyward. "That was a bit of a surprise."
"A bit?" Her voice squeaked. "The five-foot doors didn't tip you off?"
"They were a bit low, I grant you."
"And the toilet signs with antennae..."
"Might have been graffiti."
"...And three genders..."
He shook a finger at her. "Now that's not as odd as you might think. There's an evolutionary offshoot of humans that begins in the 327th century. At the end of the Third Reproductory War, the final treaty - which was signed in Guildford, by the way - resulted in genetically engineering a third gender that could mate with -"
"DOCTOR!!!" Her screech sliced through the roaring wind, cutting off his professorial monologue. He jerked back.
"Blimey, I'll never get used to that." He smiled down at his best mate. "What?"
"I'm hanging off the side of a flippin' train! Pull me up!"
"Oh. Right!" Scrambling to his feet, the Doctor trotted over and, kneeling down to hook Donna under her arms, dragged her up onto the roof of the boxcar. "There! All better," he declared, standing back up as she crawled over to cling to a strut. "Look at the view from up here! Better than the inside of the train any day!"
Lifting her head to gaze around, Donna had to admit to herself that the panorama was breathtaking. The train sped through an endless golden prairie dotted with distant clumps of trees and edged with even more distant snow-capped peaks, far off to their right. A little earlier, she'd spotted an enormous herd of what looked like wild cattle, but she'd been too busy hanging on for dear life to try to verify that they were indeed cattle and not some strange alien bovine. However, at this moment, she certainly wasn't going to give him the satisfaction by agreeing with him. "The inside of the train wouldn't be trying to sweep me off whilst I marvelled at the scenery!"
"Well, yes." He thumbed his chin as he surveyed up and down the line of cars. "Getting back in might pose a bit of a problem."
"You mean that platoon of soldiers trying to kill us."
The Doctor waved away her concern. "Not kill us. They never actually shot at us. They only wanted to arrest us, really."
"Oh, is that all?" groaned Donna, the sarcasm hanging heavy around her despite the rush of air. Feeling a bit more secure on the roof of the train, Donna sat up, though she still grasped at the strut with a hand. "Maybe next time, you shouldn't land the TARDIS inside the train's vault car."
The Doctor's eyes lit up with pride. "Oh, but did you see that landing? Inside the narrowest car on a speeding train, right in the corner, without so much as a bump or scrape!" Twirling, he punched the air in triumph.
Donna's stomach flipped as she watched him spin. "Will you sit down! I'm not having you dance yourself off this thing. You're my ride. I'd have to catch some kind of space freighter home."
Still grinning, the Doctor plopped down next to Donna. "Home, and back about four hundred and fifty years."
"That, too." She swept the hair that was now whipping over her face back and pulled it together, holding the coppery mass with one hand. "How's that, then? Aliens playing cowboys and herding cattle on one hand, and soldiers with machine guns and floaty trains on the other?"
"Maglev rail," he corrected her.
"I don't know." He gazed at the copse of trees they were currently passing as he thought. "My guess would be a strong rich government that can afford to build high-tech rail and outfit their soldiers, and a poor populace, making do with what they got, carving out their lives in a sparsely-populated land, where they have their herds and their horses and not much else."
Donna let go of her hair, the wind whipping it into a shining cloud around her face before streaming it out behind her. "Of course, we've run into the rich blokes, landing smack in the middle of their gold."
He nodded. "They're the ones that can afford to travel by maglev rail."
She rolled her eyes. "And so we're on the run again, with an army between us and your motor."
"Yeah?" He eyed her sidelong.
Donna grinned and nudged him with her shoulder. "Corking! Never a dull moment. So what do we do?"
The Doctor gazed at her with a fond, amused smile, then shrugged in response. "The way I see it, we have two choices. We can go back in and try to make our way back to the TARDIS. Not the way we came out. That'll be guarded. But see over there, on that other car? There's a panel on the roof we can open. Drop down in there, make our way back to the vault car, and, well, get arrested and spend the rest of the trip in chains."
Pursing her lips, Donna nodded sagely as she considered the course of action. "Not the most optimistic plan. And the other?"
"Sit up here, enjoy the spectacular scenery, and the company, too, mind you, until the next stop, at which point, the soldiers come out and arrest us, and we spend the rest of the trip in chains." He slipped an arm around her shoulders and squeezed.
"Brilliant,” Donna groaned, leaning into the hug. “Well, I don't see that there's much choice, really."
Jumping up together, the Doctor took Donna's hand and they ran across the roof to the other car. A quick application of the sonic screwdriver loosened the panel and, pulling it open, the Doctor helped Donna climb down into the dubious safety of the interior of the train.