It was winter, 1879.

Theresa Herondale stood by the library window of the London Institute, watching the snowflakes flutter delicately from the gray sky to coat the front lawns in a thick layer of fluffy white down.

Henry Branwell, his coppery hair a fiery ball of flame against the stark white of the snow, was slouched in his custom-designed wheelchair, cradling a bundle of blankets as if they were precious china. Only Tessa knew better—his child, Charles, was enveloped in those blankets, a soul much more fragile and precious than any china could compare. Several days had passed where snowfall was a constant companion, and Henry, much to Charlotte's despair, had taken Charles and commanded Sophie—poor, softhearted Sophie—to wheel him out onto the vast lawns adorning the Institute to admire the snowfall.

Only now, with Charlotte at a Council meeting and Tessa, Bridget, and Cyril as the only occupants of the Institute, Henry had been abandoned to lie in wait for their long-awaited return. Tessa knew she ought to urge Henry to return inside out of the bitter cold, but she doubted he would appreciate her approach.

The Institute had gotten a call from the Enclave earlier in the day to ask the Shadowhunters to aid them in a raid on a vampire clan up in Whitechapel. There had been whispers occurring in Downworld about suspicious goings-on with the vampires recently—mysterious murders, mutilated bodies, missing person reports. Cecily had been the one to insist on aiding them. Will, unable to dissuade her, had instructed Gabriel Lightwood tag along. Of course, as often the happenstance with siblings, Gideon had seen to it that Gabriel would not be facing a clan of vampires alone, with Will Herondale.

Tessa recalled drawing back the thick velvet curtains in the library window to watch as the five of them sauntered down the steps, but her eyes, as they always did, trailed to Will. As if he had sensed his gaze on her, he had turned to glance up at the library, as if anticipating, without a shadow of a doubt, that she would be there.

Tessa's heart had contracted in her chest. It was still baffling to have someone know the deepest parts of her soul, to feel as though she truly belonged in the world, after she had endured such a long time believing that no one would ever, could ever, understand her. It was terrifying yet thrilling, both at once.

That had been hours ago. The snow hadn't even begun to fall when they had left.

With a resigned sigh, Tessa let the curtain fall shut and turned away.

Since their marriage, Charlotte had ordered relentlessly that Tessa and Will share a room. Tessa had immediately turned beat red at the suggestion. Of course, it wasn't as if she and Will hadn't occupied a bedroom before; they had, numerous times. There had just been something about the thought that had seemed almost … intimate. Perhaps it had simply been like that because it was Charlotte who had suggested it.

Despite Will's enthusiasm, he had stubbornly abstained from abandoning his own room.

Tessa strode toward it now, as she had so many nights before, but with only Will beside her, their fingers laced together in a reassuring manner.

Will wasn't here to reassure her now, though, or to keep at bay the nightmares that so torturously haunted her sleep. Nightmares, of her brother, Nate, dying in her arms, his blood staining her hands; and of Mortmain, tormenting her with information about her past that she herself did not know; Agatha, and the skull-cracking screech that had escaped her when the automaton had loomed up in front of her—its bladed arm slicing through her as smoothly as a blade cutting through cheese—

"Tess."

She jerked awake at the gentle pressure on her arm, gasping as if she had been drowning. Her copy of Great Expectations thumped to the floor. The bedside lamplight was glowing dully on her nightstand, and as she turned at the sound of her name in the shadows, she smiled faintly up at the wild-haired boy beside her.

The wildness of his hair was nothing more than an assumption, Tessa guessed, for the only thing she could glimpse of him were his eyes. They shone like blue lanterns in the darkness.

"Tess," he said, and she shuddered as his warm breath stirred her hair. He reached out with his hand and ran his fingers down her cheek, gently, so gently. "Blasted nightmares. I wish I could keep them astray, keep them from hurting you—"

A small explosion of questions went off in her head, all of which she dismissed. She had been worried out of her mind, but he was here, and that was all that truly mattered. Instead, she said, "There is one thing you could do to keep the monsters at bay." And she seized the material of his shirtfront, and pulled him down on top of her.

A spark of electricity shot through Tessa's entire body as their lips brushed, a sizzling bolt of energy that pulsed down to her core. She felt her body respond to his—

And he pulled away, breaking the kiss, shattering the moment into fragments.

His voice, when he spoke, was rough with restraint.

"Wait," he said. His eyes gleamed with such intensity that their luminosity cast over the smooth skin of his cheeks. "Will you come with me, Tess? There is something I wish to show you."

Tessa frowned up at him. He was acting peculiarly odd, she thought. "Will—"

"Please, Tess," said Will. "You do trust me, don't you?"

Now her eyes widened into incredulous sorcers. It was such a bizarre question, one he himself already knew the answer to, yet he had asked it with such genuine curiosity and vulnerability that it was all Tessa could do to sit up and take his hand, and let him guide her from the room.

He guided her to the stables adorning the rear end of the Institute, drawing his hand out of hers briefly to pluck her travelling cloak from its hook and draw it over her shoulders before entwining their fingers again.

The stalls were dimly lit; the gas lamps sitting at intervals in little nooks in the stone walls sputtered brightly as soon as Will walked over the threshold. Tessa trailed more cautiously behind him, unknowing, for the first time since she had known him, what was going on beneath those thick black curls of his.

Was he intending on letting the horses loose?

"Will, what on earth—?"

Tessa's words dried up in her throat as she watched her husband saddle up the stocky black stallion, somewhat unceremoniously. Balios made a noise of protest and whipped his head around, but apparently thought Will was far too pretty to inflict real damage upon.

Will glanced back at her from over his shoulder, and Tessa's breath hitched in her throat. A memory surfaced in her mind: Tessa, striding purposely into the library with the words "This is the last I want to hear of you calling Jem at the most minor injuries imaginable!" on an endless lapse in her head, but she hadn't gotten that far, because as soon as she she'd pushed open the doors Will had jerked his head up from where it had been absorbed in a book, and she had been rewarded by catching him by surprise.

That startled expression, with his full lips parted slightly in expectation, his thick black locks tumbling over his face as if in a faint breeze, the sheen of sweat glistening at the base of his throat, where his pulse pounded—it had frozen her in place, turned her completely immobile like that of one of the statures in the gardens.

His beauty never ceased to take her breath away.

She found herself gasping now as she stared at him, mezmerized by the vulnerability stripped bare in his eyes—those eyes, their blue depths shimmering—and the upturned collar of his coat, shielding his ears from the cold snap—his breath blowing out in white clouds—

"Tessa?" he said.

Tessa blinked and refocused. The slow smile forming on his lips had faded into a frown. Will, ever the observer, could detect her emotions better than herself.

She pulled the cloak tighter around her shoulders as he pulled away from Balios and moved toward her. She saw his lean shadow pass over her boots—and then he was in front of her, gripping her shoulders gently yet with an urgency that made him dig his fingernails into her skin.

"What is it?" Will said, softly. "There's something wrong. I know there is."

Tessa glanced up and met his eyes. She smiled a genuine smile. "What could possibly be wrong?" she said. Reaching up, she caressed his cheek with the palm of her gloved hand. He exhaled, slowly, and closed his eyes. "Nothing is ever wrong when I am with you, Will." She pursed her lips. "There are two kinds of love in this world: one where the person you love anchors you to who you are and one where you forget who you are when you are with them. We are the latter," she said. "Will, I forget who I am when I am with you, because all I can think about is you, for there simply isn't enough room for anything else."

Will opened his eyes with such slowness Tessa would have assumed he was exhausted if she didn't know any better. He looked at her as she had seen only once before, on a night not too long ago, when the moon hung over their heads like a silver coin; a boy with a shock of silver hair, a press of lips against the back of her hand, her heart in her mouth. Those same blue eyes looking up and away from her, as if the moon held all the radiance of the sun.

Only, he did not look away now.

He continued to stare at her as if he had just woken out of a dream and wondered if it had been real. He swallowed visibly. "I—" He lowered his head and pressed a kiss to her temple, his long lashes tickling her face. When he pulled away, he smiled wonderingly. "I love you," he whispered. "I love you, so incredibly much."

"I love you, too. And, Will?" Tessa added, suddenly recalling what he had said to her earlier. "What is it you wanted to show me?"

And at that, a devilish smile curved his lovely lips.

"Oh—oh no," said Tessa. Her heart plummeted, its drumming pulse pounding through her ears. "By the Angel. Will, I'm going to fall—"

"You fell for me," said Will, behind her, but she felt the reassuring muscles of his arms tighten about her still. "And I caught you. And it seems as though I am the only handsome fellow worthy of your love, Mrs Herondale, unless of course you plan to divorce me after this and rebound with Six Fingered Nigel—"

"In that case," interrupted Tessa, suddenly not wanting to hear any more of Six Fingered Nigel, "then you will not be subject to a bottle of gin smashed over your head."

His silent laughter reverberated into her back, his warm breath tickling her throat. She knew she ought to open her eyes, that the jostling of the horse beneath her would not nauseate her as such if she did, but the thought of Balios, glamoured as he was, almost ploughing through the townspeople made her stomach clench.

It didn't take long to reach Will's destination. Tessa felt only the slight swerve of movement as Balios turned, could hear only the muffled thumps of the horse's hooves hitting the snow, and could smell nothing but the sweet scent of burned sugar drifting through the bitter air from distant factories. Will's arms were around her, protectively, even as he steered the horse up a steep incline. Tessa noted that the sound of hooves thumping against the snow was replaced by the squelching sound of soft earth, and a damp smell settled all around her, full of greenness and life, like a forest after a heavy downpour.

She felt as the ground levelled out beneath her. Will brought Balios to a halt, and now the only sound was the warmth of his breath on her cheek. She shuddered.

"Open your eyes, Tess," he whispered.

She did—and drew in a gasping breath.

It looked just like any ordinary forest: thick wet-dampened tree trunks soaring to impossible heights, dense green undergrowth pocked with fat mushrooms. But it all was all impossibly bright, glowing with a luminosity that made Tessa think this forest did not belong to the mundane world.

The slippery moss coating the forest floor shone a brilliant lime-green, glittering as if its surface was coated in layers of diamonds. The mushrooms gave off an almost slippery sheen, brown and ugly in luminance of everything. The leaves on the trees all around them glistened a peculiar spring-green, despite the winter weather, and the trunks of trees glowed from within their echoing depths, as if lit by from inside. Small shapes were darting through the air; Tessa caught the flash of wings in the luminosity of the moss, turning it a shade of green before it disappeared once again into the shadows.

It was beautiful and otherworldly.

Tessa stared.

"It's called Butterlight Forest," murmured Will in her ear. His breath stirred her hair. "Once upon a time, a gathering of faeries were slaughtered here. Years after their blood seeped into the roots of the earth, strange things grew where they had fallen. Not a particularly warming story, but it really is very beautiful."

Tessa's insides seemed to freeze. She remembered striding through the park with Jessamine, and the words "Here is strange earth. If your angel blood should fall upon it, golden vines will grow from the spot, with diamonds at their tips." Tessa swallowed audibly.

She started when she glanced down and saw Will had already dismounted the horse, abandoning Tessa to control the animal if it chose to gallop off with her. Impulsively, she sucked in her breath as she swung her leg over the horse's head and dropped awkwardly toward the ground—

And Will caught her. His arms wrapped about the backs of her knees and supported her back as she fell. "Are you alright? You should have waited. I would have helped you down—"

"There's no need for that." She felt her cheeks burn with humiliation as she dislodged herself from his arms. "What on earth are we doing here, Will? I do not know why you would think to drag me out here in the middle of the night, the night before Christmas, I might add, just to tell me some horrid tale about dead faeries—"

Startled light flared deep in his eyes. "I never intended to hurt your feelings, Tess," he said. "There is just something I wish to show you. Take my hand." He held it out for her.

She took it without hesitation, without question; for it was impossible to stay mad at the person you loved for long.

Sunken deep into a gathering of towering trees was a massive rock, its surface covered in thick layers of glittering green moss. Will guided her around it, to where a small lake rippled noiselessly and reflected back the forest. Will sat down on the damp ground and motioned for Tessa to do the same. She wound up in his lap, his legs shielding her own from the perishing ground beneath. Will didn't seem to mind, either way.

Tessa stared out across the shimmering expanse of the lake. The world was quiet here, the only sound being their harsh breathing and the faint flutter of wings from overhead. Tessa frowned, craning her neck—

And then Will made a whistling sound. It sounded almost like a lullaby, and Tessa was momentarily reminded with a sickening sensation in her stomach of Jem, his beautifully sculpted face peaceful and content in the moonlight of the music room as he had played for her, speaking of love and passion.

A sad smile played about her lips as she listened to the sound of her husband's melodic whistling, her eyes lulling tiredly—

And then brilliant blue light blazed up before her, casting its beam across the water, shedding its light across Will's face, reflecting in his eyes.

It took Tessa a baffling moment to realize the brightness was emanating from the hundreds of flying insects overhead, darting across the lake like fireflies. No, not insects at all—butterflies. Dozens of them. Twirling through the air delicately, glowing as bright as fallen stars.

Tessa's heart squeezed at the sight of such beauty.

"Butterlights," said Will.

Tessa whirled around to stare at him. He was grinning. A sheen of blue etched out the hollows of his elegant cheekbones, casting his eyes in shadow. "It's beautiful," she whispered, because it was. "Thank you."

The boy's grin softened into an affectionate smile, one only that spoke the language of her heart. He leaned down toward her, his hair tickling her cheek, and pressed a delicate kiss to her lips. Tessa leaned into the kiss, twisting around in his lap, her legs straddling his hips as her fingers wound into the thick coils of his hair. Her heart pounded in her ears.

When he pulled away, he rested his cheek against hers. "Merry Christmas," he said. "Tessa."

Tessa smiled. She remembered her first day at the Institute, when she had lost her way around its symmetrical corridors and Will had found her. She remembered when she had insisted he call her by her maiden name, and how she had melted at the sound of her name on his lips. She smiled now, recalling the memory. "Will," she whispered, and she felt his laughter shake his body, and she realized that for the first time, he was remembering, too.