Two Shadowhunters trudged wearily through the streets of London. Thick brown fog clung to their clothes and cast a damper over the neighbourhood. Everything was silent and still. The usual illicit late-night activities had ceased. Even the demons were too dispirited to be out in the chill.

"This patrol was such a waste of time," Will griped. His breath left icy flecks on his scarf. Jem, his companion, said nothing. "It's fine for mundanes in their bloody carriages," he continued. "Wish we could patrol in a carriage. I'd kill for some nice hot mulled wine right now, wouldn't you, Jem? Do you want to nip into the tavern before we go home?"

"Are you mad, Will?" Jem inquired, his voice muffled by his scarf, which was pulled as high up around his face as possible. "I want to get home where it's warm and dry."

"It's warm and dry in the tavern, too. And with all the fellows there, it's just like home. Especially if Saucy Susan's about. She can warm anyone up in no time. I'm sure she can find a friend for you too. You'll be so warm, in fact, that you can't help but take off all your clothes." Will cast a cheeky glance at Jem. "Of course, it'll be no bother taking these wet things off. It's putting them back on again that could possibly be disagreeable. But you know what they say – if you're warm on the inside, then it doesn't matter what you've got on. That's how sailors survive falling into icy water."

"I don't know what you're babbling on about, Will, but would it be asking too much to request that you stop?" Jem interrupted.

"I'm trying to make the time go by faster," Will protested. "But I see my efforts are in vain. Oh how the worm has turned. You have replaced me in your thoughts. My delightful chatter is no longer enough for you."

Jem rolled his eyes. "Yes, you have been replaced by a vision of a fire and a hot bath. Do stop talking, Will. Doesn't the fog stick to the back of your throat when you speak? It does mine, even through this scarf."

Will stopped to consider then made a great show of clearing his throat. "This blasted fog!" he cursed, only managing to let more particle-filled air in. Jem had to bang on his back to get him to stop choking. He wrapped Will's scarf securely around his neck and mouth, effectively gagging him, and marched him quickly down Chancery Lane and towards Fleet Street.

The abandoned ruins of the Church of All-Hallows-The-Less loomed menacingly out of the darkness. But to Jem, it was a sight for sore eyes. When he passed the gate, the broken stones faded away to reveal a magnificent castle-like structure. The London Institute, the largest in Europe, never failed to impress. Its towers soared to the sky, held up by the gargoyles and statues of angels. Yellow light twinkled homely from several un-curtained windows, drawing the weary boys in.

The front door opened easily under Jem's touch. He used the door mat to wipe sticky black mud from his shoes as he entered, then made a beeline for the fireplace. He had to thaw his numb fingers before making any attempt to remove his outerwear. Moisture began dripping uncomfortably from his clothes when the indoor warmth met him. He made a mental note to apologise to Sophie for the mess.

Will, however, had no such compunctions and began shedding layers the instant he walked through the door. He dropped his coat, hat, gloves and scarf on the floor, heedless of the puddles. "I'm off for a nice hot bath," he announced, walking off and leaving a trail of bootprints behind him.

"Enjoy your evening," Jem called after him. He considered if he should add Will's mess to the list of things to apologise for. He continued to stand by the fire, flexing his tingling fingers as feeling returned to them. He heard the patter of approaching footsteps. "Did you forget something, Will?"

"It's not Will." The tall figure of Tessa stepped into the light. "Where is he though? I wondered if the two of you might like to join Jessamine and I in the drawing room. We thought it would be nice to spend some time together. After all, it's Christmas Eve."

"Is it?" Jem asked. "It completely slipped my mind. That would explain the many mundanes we saw out and about earlier."

"So, you'll come? We've been waiting hours for your patrol to end."

"Could I change out of my gear and possibly have a bath first?"

Tessa laughed. "Of course you can. How inconsiderate of me. Just come down when you're ready. I'll go and find Will."

"He's in a mood."

"He's always in a mood. Don't worry. I can manage him." Tessa turned to go, but paused. "The gathering… It's casual. Wear your night clothes. It would be like a sleepover."

"Night clothes? That doesn't sound decent. What's a sleepover?"

"It's an American concept. It's when a group of friends gather to spend the night together. Don't worry. It's just to sleep. Not to have an orgy."

Jem blushed hard. "No… none of that…" he stammered. Tessa laughed again and left.

It was nearly an hour before Jem was ready. He wore his night clothes, as he had been told, and wrapped his dressing gown snugly around him. The stone hallways were cold and dark as he made his way down to the drawing room by the light of his witchlight. His eyes widened when he pushed open the door. The drawing room was decorated with sprigs of holly, ivy and mistletoe. Strings of golden tinsel and colourful paper streamers hung from the windows and the chairs. A roaring fire filled the room with warmth. Little paintings showing scenes of life in the Institute and London covered the mantle. A table by the fire held a large teapot, cups and a tray of food.

Church the cat was sprawled out and asleep on the hearth rug. Tessa and Jessamine sat in armchairs, one reading a book, the other staring dreamily into the fire. Both were in their nightdresses, with dressing gowns draped easily around their shoulders. Jem blushed again. He cleared his throat to announce his presence. "This is festive," he remarked.

"Thank you. I spent all day decorating," Jessamine said cheerfully. "Come, have a seat." She gestured to the sofa between the armchairs. "Where's your other half?"

"Didn't you tell him to come down, Tessa?"

"I did, and he said he would."

"Well, he's late," Jessamine pouted.

"To be fair, we didn't exactly set a time," Tessa clarified. "I just told him to come down once he'd finished his bath."

"That might take a while," Jem quipped. "Will does enjoy his baths. He sits there for hours and reads his books."

"I hope his book tonight is a short one, then," Jessamine said. She got up and went to the table. "Would you like a cup of hot chocolate, Jem?"

"That sounds lovely, Jessamine, thank you." Jem took the cup she offered and had took a sip. The chocolate was smooth and rich and warmed him completely from the inside. He also accepted a piece of gingerbread to go with it. "This is delicious."

"Isn't it? I got it from Paul's this afternoon."

The drawing room door banged open and Will sauntered in. His night clothes were rumpled and his hair was dripping wet. "Evening," he greeted, sitting on the floor and leaning against Jem's leg. He stretched his feet out towards the fire.

"Will, your hair is soaking," Jem pointed out.

"That's what happens when you take a bath, Jem."

"Kindly do not lean on me until it dries. I don't fancy damp trousers."

Will chuckled and shifted so his hair was mostly on the sofa. "So, what are we doing?" He noticed the food and reached for the gingerbread. Jessamine gamely poured him a cup of hot chocolate as well. He sniffed at it. "You didn't poison this, did you?"

Jessamine rolled her eyes. "No."

"Spit in it?"

"If you don't want it, give it back," she snapped.

Jem quickly said: "The chocolate is fine, Will. Try it. You'll like it." He took another sip from his own cup to demonstrate. Will followed his lead and his eyes widened as though he had just experienced a glimpse of the divine.

"I'm glad we're all here," Tessa said. "I'd always wanted to have a sleepover, but I never really had the opportunity growing up."

"What exactly does one do at sleepovers?" Jem asked.

"We talk or play games. Since it's Christmas, I thought it would be nice to sit around a fire and indulge in some traditions."

"What kind of traditions? Shadowhunters don't have any Christmas traditions," Jem continued.

"Mundanes do. Jessamine and I have got things started. We've lit the yule log, for one." Tessa gestured at the fire. "And we've decorated, and painted some Christmas cards. Now, we ought to hang up stockings with our names on them over the fire."

Jem was bewildered. "It's a tradition to do laundry on Christmas Eve?"

Jessamine burst out laughing. "No, silly. It's for Father Christmas to put presents in when he comes."

"Is Father Christmas actually real?" Jem wondered.

"A jolly old man riding around on a sleigh pulled by reindeer and coming down chimneys?" Will chortled. "Of course he's not real. He's a story made up by parents to make children behave. If you're good, you'll get presents. If you're naughty, you'll get coal."

"I'm sure we all know what you're getting, Will," Jessamine teased.

"If this chocolate wasn't so heavenly, I'd throw it at you for that remark," Will retorted with mock sweetness.

"You'll do no such thing," Tessa admonished. "And why wouldn't Father Christmas be real? Don't Shadowhunters always say 'all the stories are true'?"

Will smacked a hand on his knee. "That settles it! Stockings it is! Mine are upstairs, but I see you've got socks on, Jem. Hand them over, like a good fellow, will you? We can split the loot four ways in the morning." He reached to grab Jem's thick blue socks.

Jem swatted Will's hand away and tucked his feet under him. "Tempting as that sounds, I think I'll pass. I prefer the certainty of warm feet now to the possibility of presents later."

"Spoilsport." Will lightly punched him on the leg. "If we hear sleigh bells and miss out on presents, I'm holding you entirely responsible."

Jem was amused. "I don't think Father Christmas would be put off by the mere lack of stockings. If you're meant to get a present, you'll get one."

Will considered this. "You may be right," he conceded. "After all, a blazing fire wouldn't stop him from coming in. All right, no stockings then. What else do mundanes do on Christmas Eve, Tess?"

Jessamine sat up and leaned forward in her chair. "I know. How about we sing some carols?"

"Do you want me to fetch my violin?" Jem offered.

"Don't be ridiculous. It's freezing outside," Jessamine admonished. "We've all got voices. Let's sing. We can all take turns. I'll go first." She began a spirited rendition of "Hark The Herald Angels Sing" and clapped along to the beat. There was applause when she finished.

"Jessamine, you have such a sweet singing voice. I hadn't noticed before," Tessa remarked.

Jessamine tossed her hair. "That's because I haven't had much opportunity to sing before now. But I did spend many enjoyable evenings singing with my dear Mama and Papa." She trailed off as she recalled the memory. "Why don't you go next, Tessa?"

Tessa nodded. "All right. This is one by an American. At least, so I've been told." She took a deep breath and began: "I heard the bells on Christmas Day, their old familiar carols play…" Her companions listened with rapt attention. Jessamine hummed a counter melody until the song ended.

"That was beautiful!" she exclaimed. "The lyrics are so moving. 'Hate is strong and mocks the song of peace on earth, good will to men'."

"It was a poem about the American Civil War, I believe," Tessa explained. "What did you think of it, Will? You like poetry."

Will frowned. "I agree with Jessamine that it's full of despair. But I liked the end – 'God is not dead, nor doth he sleep, the wrong shall fail, the right prevail'. Powerful words."

"Words that Shadowhunters could draw inspiration from," Tessa mused. Jessamine seemed pensive.

Jem turned to Will. "How about a Welsh carol next?"

Will got to his feet. "Not a problem. But you must all sing along." He started up a very familiar tune – "Deck The Halls", but in Welsh. He made them all stand and dance along. When it came to the chorus, he conducted them vigorously and refused to proceed until they sang it with enough gusto as to satisfy him. Their voices reverberated round the drawing room. Church woke up and started yowling. Will began conducting him too and cursed in Welsh when the cat ran away. By the time the song finished, everyone was rolling in fits of laughter on the floor.

"Will, that was marvellous!" Tessa wiped tears from her eyes. "I almost want to sing it again."

"Almost?" Will raised an eyebrow.

"It's Jem's turn," Tessa reminded him. "What did they sing at Christmas in Shanghai, Jem?"

Jem shook his head. "We didn't celebrate Christmas in China. I don't think I experienced Christmas until I came here. I do know the usual carols. But I must warn you, my singing voice is not as good as the rest of you…" He cleared his throat and began: "Silent night, holy night, all is calm, all is bright…"

His voice was soft and raspy, but every note was sung in earnest. Tessa moved closer and leaned against his arm, putting a hand on his knee. Will came up and snuggled at Tessa's other side. Jem reached his hand out to Jessamine. She took it, and he tugged her to sit next to him, putting his arm around her shoulders. He sang another verse. The last note hung in the air, lingering in the embracing firelight.

"Look," Tessa whispered. "It's snowing."

True enough, white flurries were visible just outside the window, dancing in swirls on the wind. The dreary pea-souper was transformed into a magical wonderland as clean white snow covered every surface. Will, Tessa, Jem and Jessamine huddled closer together. Will tugged a plaid blanket over their heads, creating a delicious cocoon of warmth.

"We should go up to bed," Jessamine said sleepily, resting her head on Jem's shoulder.

"Let's just stay here a while longer," Tessa murmured. "It's cosy."

Jem felt a furry body nestle at his neck as Church curled up and made himself comfortable against him. Will settled his head in Tessa's lap. Her hand lifted, fingers playing with his black locks.

"Merry Christmas, everyone," Jem whispered. "I'm so glad you're all here." His eyelids grew heavy.

Soon, the only sounds to be heard were the gentle breathing of four sleepers and a cat, the crackle of a warm fire, and the distant jingle of sleigh bells.

THE END