She scowled at him. "And how do you plan not to be recognized at this ball? Benedict knows your face, as do-"

Will seized the invitation out of her hand and waved it at her. "It's a masked ball."

"And I suppose you just happen to have a mask."

"As a matter of fact I do," said Will. "Our last Christmas party was themed along the lines of the Venetian Carnevale." He smirked. "Tel her, Sophie."

Sophie, who was busy with what looked like a concoction of spiderwebs and moonbeams on the brushing tray, sighed. "It's true, miss. And you let him deal with Mortmain, you hear? It's too dangerous otherwise. And you'l be all the way in Chiswick!"

Will looked at Tessa with triumph. "If even Sophie agrees with me, you can't very well say no."

"I could," Tessa said mutinously, "but I won't. Very well. But you must stay out of Nate's way while I speak with him. He isn't an idiot; if he sees us together, he's quite capable of putting two and two together. I get no sense from his note that he expects Jessamine to be accompanied."

"I get no sense from his note at all," said Will, bounding to his feet, "except that he can quote Tennyson's lesser poetry. Sophie, how quickly can you have Tessa ready?"

"Half an hour," said Sophie, not looking up from the dress.

"Meet me in the courtyard in half an hour, then," said Will. "I'll wake Cyril.

And be prepared to swoon at my finery."

The night was a cool one, and Tessa shivered as she passed through the doors of the Institute and stood at the head of the steps outside. This was where she had sat, she thought, that night she and Jem had walked to Blackfriars Bridge together, the night the clockwork creatures had attacked them. It was a clearer night tonight, despite the day of rain; the moon chased stray wisps of cloud across an otherwise unmarked black sky.

The carriage was there, at the foot of the steps, Will waiting in front of it.

He glanced up as the doors of the Institute closed behind her. For a moment they simply stood and looked at each other. Tessa knew what he was seeing -she had seen it herself, in the mirror in Jessamine's room. She was Jessamine down to the last inch, clothed in a delicate ivory silk dress. It was lowcut, revealing a great deal of Jessamine's white bosom, with a silk ribbon at the col ar to emphasize the shape of her throat. The sleeves were short, leaving her arms vulnerable to the night air. Even if the neckline hadn't been so low, Tessa would have felt na*ed without her angel, but she couldn't wear it: Nate would have been sure to notice it. The skirt, with a waterfal train, bel ed out behind her from a laced, slender waist; her hair was dressed high, with a length of pearls held in place by pearl pins, and she wore a gold domino half mask that set off Jessamine's pale, fair hair to perfection. I look so delicate, she had thought with detachment, staring at the mirror's silvered surface as Sophie had fussed about her. Like a faerie princess. It was easy to think such thoughts when the reflection was not truly your own.

But Will -Will. He had said she should be ready to swoon at his finery, and she had rol ed her eyes, but in his black and white evening dress, he looked more beautiful than she had imagined. The stark and simple colors brought out the angular perfection of his features. His dark hair tumbled over a black half mask that emphasized the blueness of the eyes behind it. She felt her heart contract, and hated herself instantly for it. She looked away from him, at Cyril, in the driver's seat of the carriage. His eyes narrowed in confusion as he saw her; he looked from her to Will, and back again, and shrugged. Tessa wondered what on earth Will had told him they were doing to explain the fact that he was taking Jessamine to Chiswick in the middle of the night. It must have been quite a story.

"Ah," was all Will said as she descended the steps and drew her wrap around herself. She hoped he would put down to the cold the involuntary shiver that went over her as he took her hand. "I see now why your brother quoted that execrable poetry. You are meant to be Maud, aren't you? 'Queen rose of the rosebud garden of girls'?"

"You know," Tessa said as he helped her up into the carriage, "I don't care for that poem either."

He swung himself up after her and slammed the carriage door shut.

"Jessamine adores it."

The carriage began to rumble across the cobblestones, and through the open doors of the gate. Tessa found that her heart was beating very fast.

Fear of being caught by Charlotte and Henry, she told herself. Nothing to do with being alone with Will in the carriage. "I am not Jessamine."

He looked at her level y. There was something in his eyes, a sort of quizzical admiration; she wondered if it was simply admiration of Jessamine's looks. "No," he said. "No, even though you are the perfect picture of Jessamine, I can see Tessa through it somehow-as if, if I were to scrape away a layer of paint, there would be my Tessa underneath."

"I am not your Tessa either."

The light sparkling in his eyes dimmed. "Fair enough," he said. "I suppose you are not. What is it like, being Jessamine, then? Can you sense her thoughts? Read what she feels?"

Tessa swal owed, and touched the velvet curtain of the carriage with a gloved hand. Outside she could see the gaslights going by in a yel ow blur; two children were slumped in a doorway, leaning against each other, asleep.

Temple Bar flew by overhead. She said, "I tried. Upstairs in her bedroom.

But there's something wrong. I-I couldn't feel anything from her."

"Well, I suppose it's hard to meddle in someone's brains if they've got no brains to start with."

Tessa made a face. "Be flippant about it if you like, but there is something wrong with Jessamine. Trying to touch her mind is like trying to touch-a nest of snakes, or a poisonous cloud. I can feel a little of her emotions. A great deal of rage, and longing, and bitterness. But I cannot pick out the individual thoughts among them. It is like trying to hold water."

"That's curious. Have you ever come across anything like it before?"

Tessa shook her head. "It concerns me. I am afraid Nate Will expect me to know something and I Will not know it or have the right answer."

Will leaned forward. On wet days, which was nearly every day, his normal y straight dark hair would begin to curl. There was something about the vulnerable curling of his damp hair against his temples that made her heart ache. "You are a good actress, and you know your brother," he said. "I have every confidence in you."

She looked at him in surprise. "You do?"

"And," he went on without answering her question, "in the event that something goes awry, I Will be there. Even if you don't see me, Tess, I'll be there. Remember that."

"All right." She cocked her head to the side. "Wil ?"

"Yes?"

"There was a third reason you didn't want to wake up Charlotte and tell her what we were doing, wasn't there?"

He narrowed his blue eyes at her. "And what's that?"

"Because you do not yet know if this is simply a foolish flirtation on Jessamine's part, or something deeper and darker. A true connection to my brother and to Mortmain. And you know that if it is the second, it Will break Charlotte's heart."

A muscle jumped at the corner of his mouth. "And what do I care if it does? If she is foolish enough to attach herself to Jessamine-"

"You care," said Tessa. "You are no inhuman block of ice, Will. I have seen you with Jem-I saw you when you looked at Cecily. And you had another sister, didn't you?"

He looked at her sharply. "What makes you think I had-I have-more than one sister?"

"Jem said he thought your sister was dead," she said. "And you said, 'My sister is dead.' But Cecily is clearly very much alive. Which made me think you had a sister who had died. One that wasn't Cecily."

Will let out a long, slow breath. "You're clever."

"But am I clever and right, or clever and wrong?"

Will looked as if he were glad for the mask that hid his expression. "El a,"

he said. "Two years older than I. And Cecily, three years younger. My sisters."

"And El a . . ."

Will looked away, but not before she saw the pain in his eyes. So El a was dead.

"What was she like?" Tessa asked, remembering how grateful she had been when Jem had asked that of her, about Nate. "El a? And Cecily, what kind of girl is she?"

"El a was protective," said Will. "Like a mother. She would have done anything for me. And Cecily was a little mad creature. She was only nine when I left. I can't say if she's still the same, but she was-like Cathy in Wuthering Heights. She was afraid of nothing and demanded everything.

She could fight like a devil and swear like a Bil ingsgate fishwife." There was amusement in his voice, and admiration, and . . . love. She had never heard him talk about anyone that way, except perhaps Jem.

"If I might ask-," she began.

Will sighed. "You know you'l ask whether I say it's all right or not."

"You have a younger sister of your own," she said. "So what exactly did you do to Gabriel's sister to make him hate you so?"

He straightened. "Are you serious?"

"Yes," she said. "I am forced to spend a great deal of time with the Lightwoods, and Gabriel clearly despises you. And you did break his arm. It would ease my mind if I knew why."

Shaking his head, Will raked his fingers through his hair. "Dear God," he said. "Their sister-her name is Tatiana, by the way; she was named after her mother's dear friend, who was Russian-was twelve years old, I think."

"Twelve?" Tessa was horrified.

Will exhaled. "I see you have already decided for yourself what happened,"

he said. "Would it ease your mind further to know that I myself was twelve? Tatiana, she . . . fancied herself in love with me. In that way that little girls do.

She would fol ow me around and giggle and duck behind pil ars to stare at me."

"One does sil y things when one is twelve."

"It was the first Christmas party at the Institute that I attended," he said.

"The Lightwoods were there in all their finery. Tatiana in silver hair ribbons.

She had a little book she carried around with her everywhere. She must have dropped it that night. I found it shoved down the back of one of the chaise longues. It was her diary. Fil ed with poems about me-the color of my eyes, the wedding we would have. She had written 'Tatiana Herondale' all over it."

"That sounds rather adorable."

"I had been in the drawing room, but I came back into the bal room with the diary. Elise Penhal ow had just finished playing the spinet. I got up beside her and commenced reading from Tatiana's diary."

"Oh, Will -you didn't!"

"I did," he said. "She had rhymed 'Wil iam' with 'mil ion,' as in 'You Will never know, sweet William / How many are the mil ion / ways in which I love you.' It had to be stopped."

"What happened?"

"Oh, Tatiana ran out of the room in tears, and Gabriel leaped onto the stage and attempted to strangle me. Gideon simply stood there with his arms crossed. You'l notice that's all he ever does."

"I suppose Gabriel didn't succeed," said Tessa. "In strangling you, I mean."

"Not before I broke his arm," said Will with relish. "So there you are. That's why he hates me. I humiliated his sister in public, and what he won't mention is that I humiliated him, too. He thought he could best me easily. I'd had little formal training, and I'd heard him call me 'very nearly a mundane' behind my back. Instead I beat him hollow-snapped his arm, in fact. It was certainly a more pleasant sound than Elise banging away on the spinet."

Tessa rubbed her gloved hands together to warm them, and sighed. She wasn't sure what to think. It was hardly the story of seduction and betrayal she had expected, but neither did it show Will in an admirable light.

"Sophie says she's married now," she said. "Tatiana. She's just getting back from traveling the Continent with her new husband."

"I am sure she is as dull and stupid now as she was then." Will sounded as if he might fal asleep. He thumbed the curtain closed, and they were in darkness. Tessa could hear his breath, feel the warmth of him sitting across from her. She could see why a proper young lady would never ride in a carriage with a gentleman not related to her. There was something oddly intimate about it. Of course, she had broken the rules for proper young ladies what felt like long ago, now.

"Will," she said again.

"The lady has another question. I can hear it in her tone. Will you never have done asking questions, Tess?"

"Not until I get all the answers I want," she said. "Will, if warlocks are made by having one demon parent and one human parent, what happens if one of those parents is a Shadowhunter?"

"A Shadowhunter would never all ow that to happen," said Will flatly.

"But in the Codex it says that most warlocks are the result of-of a violation," Tessa said, her voice hitching on the ugly word, "or shape-changer demons taking on the form of a loved one and completing the seduction by a trick. Jem told me Shadowhunter blood is always dominant. The Codex says the off-spring of Shadowhunters and werewolves, or faeries, are always Shadowhunters. So could not the angel blood in a Shadow-hunter cancel out that which was demonic, and produce-"

"What it produces is nothing." Will tugged at the window curtain. "The child would be born dead. They always are. still born, I mean. The offspring of a demon and a Shadowhunter parent is death." In the little light he looked at her. "Why do you want to know these things?"

"I want to know what I am," she said. "I believe I am some . . . combination that has not been seen before. Part faerie, or part-"

"Have you ever thought of transforming yourself into one of your parents?"

Will asked. "Your mother, or father? It would give you access to their memories, wouldn't it?"

"I have thought of it. Of course I have. But I have nothing of my father's or mother's. Everything that was packed in my trunks for the voyage here was discarded by the Dark Sisters."

"What about your angel necklace?" Will asked. "Wasn't that your mother's?"

Tessa shook her head. "I tried. I-I could reach nothing of her in it. It has been mine so long, I think, that what made it hers has evaporated, like water."