For the first hour, Jack was terrible—and would have been whether or not he'd lingered on the Faculty roof to observe her technique. He was out of shape, and he had to stop every few moments to gawp at Ellini as she scampered over the rooftops like a scrap of black silk in the breeze.

She was amazing. There was something—well, if not graceful, then at least strong, about her movements. Skinny and wretched and glistening with sweat, like the girl who couldn't stop dancing in The Red Shoes. But she had turned her wretchedness to good effect, and now it made her powerful.

She vaulted over statues and chimneys, obstacles that the gargoyles behind her couldn't dodge as quickly. Sometimes she would suddenly duck, or change direction, or appear to drop completely off the edge of a roof, causing the gargoyle pursuing her to skid to a halt and overbalance.

There were six or seven of them now. He couldn't be sure of the exact number, because they looked identical, and they spaced themselves evenly across the rooftops, ready to jump out from behind a chimneystack and snap at your ankles as you ran from their companions. Jack couldn't help feeling that they'd be more effective if they all attacked at once, but he couldn't deny that they were hardy creatures. Even the ones who fell fifty feet onto the cobbles were up and snarling again in a matter of moments.

But Ellini was right. You didn't have to be quick, you just had to be inventive. And the rooftops of Oxford were so varied—so full of ledges, recesses, outcrops, and sudden drops—that there was always a new route to discover. Pathways blossomed out of the dark that seemed to have been designed just for him.

And he noticed other things too, now that he was out of the Faculty, with all its closed windows and bright, blinding lights. He couldn't believe how much there was to notice, and how much of the world he'd been ignoring up till now. He noticed the darts and crossbow bolts that occasionally clattered off the brickwork where Ellini had recently passed by. There were people trying to kill her on the ground as well. Whoever was in charge of pursuing her was clearly getting desperate.

Even if she didn't kill herself on the fourth of July, it would be such a mission to keep her alive. It would involve thinking and planning and fighting and watching every second of the day. It would be like an intricate game with the entire city as the board, and real, moving pieces that he could fight. It would be wonderful.

Jack didn't try to fight the gargoyles. He had promised both Ellini and Alice that he wouldn't. But there should be some kind of goal besides getting away from them, shouldn't there? Ellini had explained that there was no way to hurt them, but you could inconvenience them, surely? You could show them you had teeth.

By the end of the first hour, he'd devised his own scoring system. Five points if you could make them lose their balance—ten if you could make them fall—twenty for any kind of physical blow. A kick which resulted in the creature staggering and falling could earn you thirty-five points in a matter of seconds.

His favourite part—although it only scored a ten—occurred towards the end of the night, just when the drizzle and the approaching dawn were starting to drive all but the most committed of spectators back towards their homes.

He was racing over the copper tiles of the Bodleian's roof, when on impulse he swung down over the ledge that overlooked the courtyard, dangling there one-handed, while the gargoyle, over-reaching itself in an effort to grab him, tumbled onto the cobblestones below.

Ellini saw, he was sure of it, because the next time they met up, on the roof of the Sheldonian theatre, she was avoiding his eyes with increased determination.

"See that?" he said proudly, as they sheltered behind the little white cupola that formed the apex of the theatre's roof. "My one's limping."

Ellini—still panting—gave him an exasperated smile. "You're a natural."

At that moment, a claw swiped out from the other side of the cabin, catching and shredding the hem of Jack's coat. As one person, he and Ellini got to their feet and dashed off again, lungs burning.

And somehow, she could always anticipate him. She slipped easily into his arms when he threw the grapple and swung from the roof of the Sheldonian onto the Ashmolean building. When he changed direction, she found a way to follow.

She always knew what he was trying to do. It was as though they were dancing, and she was—somewhat reluctantly—letting him lead.

They ran from the Ashmolean, over the rooftops of Exeter College, to the flat, copper-slate roof of the Turl Street Music Rooms. Here, there was a flagpole sticking out horizontally from the slightly taller building behind. Ellini saw him giving it a calculating look and acquiesced without comment when he grabbed her by the waist and lifted her up to reach it.

It was one of those perfect moments. He spent his whole life trying to recreate them, when he counted blinks, and tapped his feet, and tried to juggle twelve different tasks at the same time. Everything seemed to come together from all directions and collide to form a perfect whole.

Ellini gripped the flagpole and swung herself up like a trapeze artist. Jack didn't have much time to dwell on that sinuous motion, because the gargoyle was behind him now. He could feel its ragged breath on the back of his neck.

He ran to the edge of the roof, and then stopped, turned round, and waited. The gargoyle was still bearing down on him, scrambling across the roof on its hands and feet, taking deep, nasal breaths as though hoping to sniff him up. He only had a few seconds.

He was already ducking when he saw Ellini swing down on her grapple. Her bare feet collided with the creature's back, and knocked it, flailing, off the edge of the roof.

For one horrible moment, Jack thought the creature would succeed in grabbing Ellini's ankle as it fell, but she tucked her legs in just in time, and continued to swing out over the darkness while it plummeted.

He peered through the gaps in the balustrade at the edge of the roof and saw the crowd below scatter as the demon came hurtling down.

It tried to get up—hah, it couldn't—and flailed out at a few rapidly-retreating ankles as it staggered. The 'Bride of Satan' man dropped his placard and fled.

Ellini swung back and dropped onto the slates beside him, panting and giggling. She didn't protest when he pulled her down onto the slates, bundling her under the balustrade and out of sight.

They lay there for a moment, laughing with as much breath as they had.

"Did the crowd get away in time?" Ellini whispered.

"I'm afraid so," said Jack, peering once again through the gaps in the balustrade. "You were aiming for the man with the 'Bride of Satan' placard, weren't you?"

"No!"

Jack continued to squint down at the gargoyle. "Oh, he is going to ache tomorrow..."

"What's he doing?"

"Well, he's using that big doorknocker on Jesus College to pull himself up. Now he's sniffing the air. Now he's making a very rude gesture with his claws—"

"Oh, he is not," she protested, craning round so that she could see through the balustrade for herself.

Jack hurled a peppermint phial into the alley to make sure the gargoyle didn't pick up their trail again, but it was probably unnecessary. Dawn couldn't be far off, and the creatures would soon be slinking back to whatever rock they crawled under during the day. Some of them would even be limping to it.

"You know, you should join the circus," said Jack, leaning back against the balustrade. "You'd be bloody marvellous on the trapeze."

Ellini shook her head. "I'm an escape artist, remember? Top hat and tails and everything. The Great Ellini."

Jack didn't know what she was talking about, but she was so luminous in that instant, so happy and excited, that it was almost painful to watch. He could see her chest rising and falling. He could see her trying to avoid eye-contact with him in case it revealed too much about her emotional state. She needn't have bothered. Even her feet spoke volumes about her emotional state at the moment.

He had to kiss her. This time, his left arm didn't even play any part of it. He leaned forward, his heart thumping for reasons he couldn't begin to understand, but she was too quick for him.

"Don't," she said, turning her head, so that his lips came to rest against her cheek. "Don't." She planted a kiss beneath his eye, and another on his forehead, laughing the whole time. "Don't make me think about things—I'm so happy." She rolled onto her front, propping up her chin in the palms of her hands, and lay there with her eyes closed, savouring the piano music welling up from the floors below. "Let's talk about Orpheus," she said. "Tell me what you know about Orpheus."

Jack, who felt happy and bewildered and vaguely annoyed, tried to focus on the question. "I know he played the lyre and not the piano."

"Oh, you've been living in this city of pedants much too long," she said, her face still glowing with happiness. "Let me tell you a story about Orpheus, then. Let me tell you how he rescued me from the Underworld. It was about eleven years ago, in Edinburgh. I was living at Pandemonium, but I didn't spend a lot of time there. I was too strange and ill-groomed for the ballrooms, and I couldn't always sneak into Myrrha's library to bury my head in a book, so I used to spend most of my time clambering over the Edinburgh rooftops. Isn't that funny? Eleven years before I'd even heard of Charlotte Grey, and I was scampering over the rooftops of my own accord."

She paused, listening to the tinkling, aimless, liquid notes. "Anyway, sorry, that doesn't have anything to do with Orpheus. Let's get back to him. I was climbing over the roof of the Assembly Rooms in St. Andrew's Square." She paused and glanced at him for a second, her eyes sparkling. "Do you know them?"

"Ye-es," said Jack slowly. It felt as though the memory was buried under great, groaning heaps of junk, but it was reasonably easy to unearth. "I played there, didn't I? Eleven years ago."

Ellini beamed. "I'm so glad you can remember! It was one of your best concerts—and I should know, because I went to eight more after that."

"I'm confused."

Ellini waved a hand impatiently. "All you need to know for the purposes of this story is that I heard your music from the roof of the Assembly Rooms. In fact, it was so good that I climbed down from the roof and sat on the outer-ledge of a third-floor window. I'd never heard anything like it."

She broke off again, to listen to the music vibrating underneath them, and Jack began to suspect—with some annoyance—that she had heard something like it, and that it was currently depriving him of her undivided attention.

"You have to understand what an awful mess my brain was in back then," she went on. "It had been a few years since Robin killed my family, but I still couldn't stop thinking about it. Ever since the first murder—that was my little sister, Sita—I'd been torturing myself, thinking of all the things I could have done to prevent it, and all the stupid things I did to ensure it. I don't think I'd had a single moment's peace till the night I heard you play. And then, suddenly, hell wasn't hell anymore. Just like I said this morning. 'Tantalus made no effort to reach the waters that ever shrank away. Ixion's wheel stood still in wonder, the vultures ceased to gnaw Tityus's liver, the daughters of Danaus rested from their pitchers, and Sisyphus sat idle on his rock'."

Jack blinked. "All those people were in your head?"

"In a manner of speaking. And for the first time in what felt like forever, you'd turned my head into a nice place to be. And, you know, the funny thing is, even after you'd stopped playing the piano—because you gave up almost as soon as you met me—you went on providing me with those moments of respite. I think it's because you never said what I expected you to say. You made me feel as though perhaps I didn't have the entire world mapped out."

Jack was silent for a moment, listening to the music. He could feel the notes rising through the slates and shuddering in the pit of his stomach, and for some reason, it felt exactly like dread.

"This pianist," he said, in a hollow voice. "The man downstairs. I bet he's going to be the one to save you this time. That would be a good story."

"I'm not in that kind of story."

"Yeah," said Jack, who hadn't been listening. He was staring straight ahead. "When you meet him, he'll be like the second me." He broke off and listened again, willing the mysterious pianist to make one mistake, play one wrong note. "Only he's better than me, so I expect he won't forget you."

"It could be a woman," said Ellini playfully. "Although I doubt it would matter to me much, if she could play that well."

Jack laughed. "OK. You've just reconciled me to the idea."

"You know, if you ever—start to remember me, or—"

"What do you mean?" said Jack, the horror creeping back again. "Why would I suddenly start to remember you?"

"I don't know—if the spell wears off or something."

"Is the spell going to wear off?"

"I don't think so," she said again. "I just want you to remember—in case you ever feel differently—that I never hated you. And I'll never be sorry I came here and saw you again. It wasn't always easy, but I wouldn't trade it for anything in the world."