You can feel like you're falling even when you're climbing up—that was one of life's punch lines. Amy balanced the heels of her trainers on a steel cord and reached down, tipping and swaying, to take River's hand and pull her onto the same wire. They rested their hands on the far wall and stared up. That's where they were going: up, up as far as the eye could see.

Even higher than the courtyard where Amy and Rory had landed.

The TARDIS would be long gone from there. It was too subtle and valuable to leave out for the elements. It was a spoil of war, even if the advance guard didn't understand exactly what it was—or what it contained. They'd take it as close to the roof as they could, so the Gorgoran leadership could take a crack at it. That meant traveling up. Thin logic, to Amy, but River was the expert. Or as close to the expert as Amy was likely to get.

So Amy and River went up, while Rory and the others went down. But Amy felt like she was treading air. She had agreed to River's plan almost silently and without complaint. Amy's obligation tugged inside her like she was a fish on a line. But how could she leave Rory? Yeah, it wasn't forever—they hoped. But every time she chose the Doctor... every time she chose this, Rory felt it. Her hand still ached where Rory usually held it; he'd gripped it like a vise since they first understood the profound danger they were all in. It felt empty now; weightless. And her lips still stung where he'd kissed her goodbye.

They'd already lost each other once. How many times could you leave someone before they started to hate you?

River's voice interrupted this sad litany. "It's difficult, isn't it?"

"Hmm?" said Amy, affecting calm.

"Leaving. Or getting left." She shrugged. "Not that there's much difference in the end."

"I'm fine," said Amy. She took a deep breath and swept a spare strand of hair behind her ear.

River smiled tightly. She used the torch she had borrowed from Amy to point out a hollow in the wall, about forty feet above them. "If we can get up there, we're back near the guards' offices. It's all short and narrow up there. We won't have to worry about falling for hours."

"All right."

That reminded Amy—part of her disorientation was due to the fact that it was a long drop to the ground. Working as a team, and never quite certain of their footing, they had climbed very high in less than an hour. Where there were no access ladders, they climbed wires. Stormcage drew a lot of power, and many of the wires were strong enough to bear the weight of two nimble women.

But not all of them.

"Careful," River didn't have to say. She reached out and tagged a wire with the end of the torch. It didn't spark so she gave it a tug with her hand. When she was sure it would bear her weight, she hooked an arm round it and sprung up, quick as an acrobat. Amy was ready and didn't stumble when the wires began to rock and twist.

River braced herself and extended a hand. Amy took hold of it. But at that moment—for no reason that Amy could see—Amy's wedding band bit sharply into her hand. She gasped and her foot slipped and both wires they were balanced on shuddered and swung as if they'd been thrown into the storm outside.

"Amy!"

They were both in danger of a deadly fall. River struggled to balanced herself. Her hand closed around Amy's wrist hard and cold as a shackle. She'd never let go of a friend to save herself; that was one way River and the Doctor were alike. One way that Amy had always feared she was different.

They stood frozen until the swinging began to slow. It took a bit longer for their own shaking to subside.

"Okay," breathed River. "Okay?"

"I'm all right," said Amy, though she felt cold and mushy inside, and her ankles ached.

"Amy, you have to be here," said River. She shook Amy's hand as if to wake her from a dream.

"Oh, I'm here," said Amy. Stretched between two wires, she had a perfect view of the distant floor. "Definitely here now," she said in a fake-perky voice.

River said. "Can you push with your feet?"

Amy tried. She was too badly balanced now; she couldn't get any purchase.

River saw and understood. "No problem," she said. She looked over Amy's shoulder again and repeated it to herself, more slowly and thoughtfully. "No problem." She made eye contact with Amy again and smiled. "What's Rory's favourite book?"

"Due respect, River," said Amy breathlessly. "Is this really the time for a book talk?"

"This could be the last conversation you ever have," said River cheerfully. "Might as well make it interesting." River looked authentically interested, like they were having a cozy little chat in a cafe.

Seeing excuse not to answer, Amy said, "We don't really have much time for reading these days." She blinked a few times. She was staring down a dark hole more than five storeys high. "I can't imagine why."

"Oh, there's always time for a good book," said River. "I'm partial to mysteries."

Amy tried to play along. "I suppose you need an escape."

"In more ways than one," said River sincerely. "Know what the Doctor's favourite is?"

Amy's ears perked up. Even with her life on the line she was always on the alert for information about her most mysterious friend. "I suppose it changes," said Amy.

"Surprisingly little."

"To Kill a Mockingbird," Amy guessed. "He is..." she paused to get her breath. "...So Atticus Finch."

"You're wrong," said River. "It's The Hitchhiker's Guide to the Galaxy."

Of course it was. Amy rolled her eyes.

"You want to know something else?" River said.

"Eh?"

"You're not thinking about your footing anymore."

Amy blinked. River felt her tense up. At the same moment River pulled up, hard as she could.

It was a good plan; River liked it. The same dreaminess that had caused Amy to lose her footing, turned to their advantage. If Amy wasn't in mortal terror of falling, her balance would restore itself; it was a natural function of the human brain.

But psychology can't trump physics—at least, not in this universe. Not yet.

At the last moment, when River was certain it had worked, when she was bearing all of Amy's weight, Amy's grip weakened.

She slipped out of River's grasp.