Jem held up his hand. His palms were scarred with runes, and Julian ached to see them—runes, in this runeless place. Insight. Quietude. Courage.

And then Jem began to change. Diana swore and yanked a pistol from her belt as a ripple went over Jem’s features and the parchment robes slid to the ground. His hair lightened and tumbled, long and waving, to the middle of his back; his eyes turned gray and long-lashed, his figure curved and feminine inside a plain gray dress.

Diana cocked the pistol. “Who are you?”

Emma had stopped in the middle of the path. She blinked back tears and said, “This is her. The Last Warlock. This is Tessa Gray.”

*

Tessa had set the inside of the cave up as cozily as possible. There was a small fireplace, whose smoke went up a flue built into the rocks. The stone floor was brushed clean and dotted with carpets; there was a small sleeping annex and multiple chairs covered in cushions and soft pillows. There was even a little kitchen with a small range, a refrigerator humming along without being plugged into anything, and a wooden table already set with teacups and a loaf of warm sweet bread.

Realizing she hadn’t had breakfast, Emma wondered if it would be a faux pas to leap on the bread and devour it. Probably.

“Sit down and eat,” Tessa said, as if reading her mind. As they settled around the table, Church climbed into Emma’s lap, rolled onto his back, and promptly fell asleep with his feet in the air.

Diana tore off a hunk of the bread and stuffed it in her mouth. She closed her eyes in bliss. “Oh. My. God.”

Emma decided that was her cue. For the next minute, she shut out the world around her and entered a blissful carb coma. The last time she’d eaten real food was in that clearing with Julian, and this was warm and home-cooked and felt like the taste of hope.

When she opened her eyes, she realized Julian hadn’t even taken a bite yet. He was looking at Tessa—that Julian look that seemed completely innocent but actually meant he was taking someone’s measure, assessing their weaknesses, and deciding if he trusted them.

It was pretty hot, actually. Emma sucked a piece of sugar off her thumb and tried not to smile to herself.

“You must be wondering who we are,” he said as Tessa poured their tea.

“No.” Tessa set the teapot down and took a seat, wrapping a shawl around her shoulders. “I know who you are. You are Emma Carstairs and Julian Blackthorn, but not the ones from this world.”

“You already know that?” said Diana in surprise.

“I see as a warlock sees,” said Tessa. “I know they do not belong here.” She indicated Julian and Emma. “And I have seen, a little, into other worlds—into their world in particular. It is closer to this one than we might like to think.”

“What do you mean?” Julian said. “They seem pretty different to me.”

“There are stress points in history,” said Tessa. “Places where a great deal of chance is at play. Battles, peace treaties, marriages. That sort of thing. That’s where timelines are likely to split. Our two timelines split at the Battle of the Burren. In your world, the demon Lilith was too weak to render Sebastian Morgenstern much help. In Thule, another demon gave aid and strength to Lilith. She was able to kill Clary Fairchild, and that’s where our timelines split—only seven years ago.”

“So this is what our world would be like without Clary,” said Emma, remembering all the times she’d heard people—mostly men—say that Clary wasn’t a hero, that she hadn’t done much that deserved to be praised, that she was selfish, even worthless, just a girl who’d been in the right places at the right times.

“Yes,” said Tessa. “Interesting, isn’t it? I gather that in your world, Jace Herondale is a hero. Here he is a monster second only to Sebastian.”

“Doesn’t he even care that Sebastian let Lilith kill Clary?” demanded Emma. “Even when Jace was in thrall to Sebastian in our world, he loved Clary.”

“Sebastian claims the death of Clary was not what he wanted,” said Tessa. “He says he murdered Lilith as revenge for her taking of Clary’s life.”

“Not sure anyone believes that but Jace,” said Diana.

“He’s the only one who has to,” said Tessa. She ran her finger around the rim of her teacup. “I must apologize for testing you,” she said abruptly. “I appeared as Jem when you arrived because I knew that the real Emma Carstairs would be delighted to see him, while anyone aligned with Sebastian would be horrified at the sight of a Silent Brother.”

“Jem . . . ?” Emma whispered. She knew what Livvy had said, that all the Brothers were gone, but still she had hoped.

Tessa didn’t look up. “He died in the attempt to seal the Silent City. It was successful, but he gave his life to hold off Sebastian’s Endarkened as the Brothers made their last stand to protect the Mortal Instruments.”

“I’m sorry,” Julian said. Emma remembered Tessa and Jem in her own world, eyes only for each other.

Tessa cleared her throat. “Sebastian already has possession of the Mortal Mirror—Lake Lyn. It is surrounded by demons, ten thousand strong. None can go anywhere near it.”

“Why is he guarding the lake so fiercely?” said Emma. “If no one can get to any of the Mortal Instruments—”

“As the warlocks were sickening, we found that the water of Lake Lyn could neutralize the blight that was eating through our world. We raced there to collect the water. But by the time we arrived at the lake, Sebastian had surrounded it with countless demons.”

Emma and Julian exchanged a look. “With the blight gone, would the warlocks have been cured?”

“We believe so,” said Tessa. “We had a small amount of the water and used it to cure the blight around the Spiral Labyrinth. We even gave it to some warlocks, mixed with ordinary water, and they began to improve. But it simply wasn’t enough. The warlocks began to sicken and turn again. We could not save them.”

Emma’s heart thumped. If the water of Lake Lyn had neutralized some of the blight here in Thule—if it had helped the warlocks, even as this world was turning to demonic poison all around them—surely the water of their own Lake Lyn, in their own world, might be a cure?

They needed to get home more desperately than ever. But first—

“We need your help,” Emma said. “That’s why we called on you.”

“I guessed that.” Tessa rested her chin in her hand. She looked young, no more than twenty, though Emma knew she was over a hundred. “Is it that you want to get back to your world?”

“It’s not just that,” Julian said. “We need to get into the Silent City. We have to get to the Mortal Cup and the Mortal Sword before Sebastian does.”

“And then what?” Tessa said.

“And then we destroy them so Sebastian can’t use them,” said Emma.

Tessa raised her eyebrows. “Destroy the Mortal Instruments? They’re very nearly indestructible.”

Emma thought of the Mortal Sword shattering under Cortana’s blade. “If you open up a Portal back to our world, we can take them through with us. Sebastian will never be able to find them.”

“If it was that simple,” Tessa said sharply, “I would have already opened a Portal, leaped through it, and taken the Cup and Sword with me. To open a Portal between worlds—that is complex, powerful magic, far beyond most warlocks. I can see into your world, but I cannot reach it.”

“But you can get into the Silent City, right?” said Emma.

“I believe so, though I have not tried,” said Tessa. “I thought the Sword and the Cup were safe there. The Silent Brothers died to protect the Instruments and to remove them would have left them vulnerable to Sebastian. Yet now he is close to breaking the seal on the doors.” She frowned. “If you can truly bring the Instruments back to your world then they would be safer there. But without the knowledge that a Portal can be opened, there is another way to end the threat.”

“What do you mean?” said Julian. “There’s nothing we could do with the Sword or Cup here, besides demonic magic.”

“People used to say that the Mortal Sword could kill Sebastian,” said Diana, her gaze sharp. “But that’s not true, is it? I was at the last battle of Idris. I saw Isabelle Lightwood take up the Mortal Sword and deal Sebastian an incredible blow. He wasn’t even nicked. He struck her down instead.”

“Ave atque vale, Isabelle Lightwood.” Tessa closed her eyes. “You have to understand. By then the invulnerability granted to Sebastian by Lilith had grown so strong no warrior of this earth could slay him. But there is something most do not know. Even Sebastian does not know it.” She opened her eyes. “He is tied to Thule, and Thule to him. A warrior of this world cannot slay him with the Sword. But the Silent Brothers knew that did not hold true for a warrior who was not of Thule. They locked the Sword away, hoping for a day when a warrior would arrive from Heaven and end Sebastian’s reign.”

For a long moment, she gazed intently at Emma and Julian.

“We’re not from Heaven,” Emma said. “Despite what some bad pickup lines I’ve heard over the years might have you believe.”