Clary sat on the couch in the Institute's library, deep in a book. It had been a quiet day at the Institute; her training was going well, and she'd only stabbed Jace accidentally eight times so far, which was good in her book.

Just then the doors slammed open.

Both Clary and Jace looked up at once, startled, as Alec stumbled into the room.

Jace got to his feet instantly. "Alec–,"

Alec staggered in, his eyes wild. He was trembling from head to toe. He grabbed Jace by the collar. "I– I can't keep going, I can't–,"

Jace took his friend by the shoulders, face deeply concerned. "What's wrong? What happened?"

A spasm went through Alec and he dropped to his knees, his pale face a mask of horror. "I – can't–,"

The room was plunged very suddenly into darkness.

Clary looked around the blackness in confusion and terror. What was going on?

A spotlight clicked on out of nowhere.

A single beam of white light spotlighted Alec, who stood with his back to them in the middle of the library's floor, standing still as a statue. Clary looked on in complete bafflement.

All of a sudden music blasted from nowhere, and Alec spun in a perfect circle to face them with one hand pointed in their direction. His outfit had somehow changed to a striped orange and black cut-off open at the neck– Clary stared on in fascinated horror– 80s clothes?

The electric guitar blasted from nowhere, all at once. Alec spread his feet and clapped his hands in an unmistakable move from the 80s. Alec began to sing then, the opening words to Eye of the Tiger.

Clary and Jace's mouths fell open at the same time.

Alec, Clary admitted with detached amazement, was an incredible singer.

The song went on, blasted through hidden speakers, as Alec danced and sung with a red spotlight trained on him. Mist, turned red in the spotlight, curled at Alec's feet. He spun and threw his hands out as the chorus came.

Clary and Jace slowly looked at each other. Clary saw her own bafflement reflected in his eyes.

"Alec can dance," Clary said, not sure if she should be terrified or impressed. Jace nodded weakly.

The two of them watched until the song ended. Alec finished with a flourish, and the spotlight flicked off, throwing the room back into darkness. And then the light came back on, and they saw Alec standing there, back in his usual black sweater and jeans, his face contorted in terror.

"I just sung Eye of the Tiger," he mouthed.

"And it was... impressive," Jace said slowly.

Clary nodded.

"What's going on?" Jace asked. "Alec, what happened?"

"I don't know," Alec whispered. He sunk down into an armchair. Clary and Jace hurried to him.

Alec sat there, staring at a spot on the wall, his eyes wide. "I don't know what happened. I was fighting this vampire, and then..."

He shook his head slowly, obviously still in a state of shock.

"What happened, Alec?" Jace prodded gently.

Alec turned to stare at Jace. "We started singing," he said.

Clary shared a look with Jace.

"You started singing," Clary repeated.

Alec nodded blankly. "The vampire and I. It was... it was Miley Cirus."

Clary gasped.

Jace looked horrified. "No."

"I don't know why, or how," Alec said. "We just stared singing. It was horrible. So horrible."

"But that's not all, is it?" Clary whispered.

Alec shook his head. "No," he whispered. "On the way here I sung a song from Glee."

"Which one?" Jace asked.

"Does it matter?" Alec said, his voice hoarse. "They're all so horrible."

Jace put a hand on his shoulder. "It's going to be okay, Alec."

Alec buried his face in his hands. It was very unlike Alec to get so upset about anything, which meant this was a very, very bad thing indeed.

"But is it just you?" Clary asked. "No one else is–,"

The doors slammed open.

Isabelle strode in, singing the last part of Uptown Girls, accompanied by more music from nowhere. She danced in with great ability, and stopped with a great flourish.

The music died and she let her hands fall to her side. She stared at them, her dark eyes huge. "What the hell was that?"

"You tell us," said Jace, whose eyes were just as huge.

Isabelle walked in somewhat unsteadily, her hair all over the place. "Oh God, you won't believe what's going on out there– it's like some kind of warped Glee episode–,"

"Is it demons?" said Jace.

Isabelle looked doubtful. "It seems a little strange for a demon."

"Maybe it's a curse," Clary suggested. "An especially powerful warlock cursed this part of New York."

"Not forever," said Jace, looking absolutely horrified.

"We'll have to move the Institute," Alec said.

"Or we just find the warlock," Clary said.

"No, it is not me," Magnus said. "If it was, nobody would be singing Cream."

"Say it was you," Jace prodded.

"Madonna, The Doors," said Magnus. "End of story."

He slammed the door shut.

The four Shadowhunters walked onto the street. Clary was getting more and more nervous– both Alec and Isabelle had already broken out into song, and they'd passed countless people singing and dancing on the street. How long would it be before she, too, was a victim? And what would she sing? Hopefully not something embarrassing.

She stopped in her tracks, feeling as if invisible hands had jerked her to a stop.

Jace turned. "Clary?"

She only had time to shriek, "Help me!" before the music started.

Oh no. No, no, no, no, no.

"I must have died and gone to heaven," Clary sung against her will, "cause it was a quarter past eleven– on a Saturday night in 1999."

Jace, Isabelle, and Alec stared at her.

She couldn't control it. She didn't understand where this voice was coming from, or where the awful, humiliating outfit had, and she wished she would stop dancing, but some outside force was controlling her completely.

She danced past Isabelle, trying desperately to reach out and grab at her, but her arms wouldn't work. The music blared in the background, horrible, absolutely horrible, and her voice rose up out of nowhere, a voice that could never have come out of her throat and yet was still hers.

"Cosmic Girl," Jace said. There was pity in his voice, but there was also amusement. Clary felt like punching him in the nose.

Clary struggled through every humiliating moment until finally it was over. Her clothes came back instantly and she almost toppled over, but Isabelle steadied her with a hand on her shoulder.

Clary saw the grin about to break free on Jace's face and saw the great, deep pity on Alec's face. Isabelle just looked grim.

"Wait till it happens to you," Clary snapped at Jace.

"So it is demons," said Alec.

"Well," said Jace, his eyebrows furrowed as he slipped his Sensor back into his pocket, "there's a lot of demon activity around people who are singing, so I'd say so."

They surveyed the terrified-looking FedEx guy for a while as he danced around, singing Can't Buy Me Love.

"But we still have to find the demon," Isabelle said.

"I think I have a rune for that," Clary announced. She produced her stele from her pocket and bent down on the pavement to carve the rune into the ground. After she was done she stood up, satisfied. They waited as the rune smoldered on the asphalt.

A Big Mac appeared in Alec's hand. He stared at it, alarmed.

"Oh, oops," she said, embarrassed. "That was the rune for instantly summoning a Big Mac. Let me try again."

This time the rune smoldered and glowed faintly with a white light. The whole world suddenly drained of all color and a trail of golden light appeared, leading from the confused FedEx guy and around a corner until it disappeared from sight.

"Wow," Isabelle said.

"Come on, it won't last forever," said Clary.

The four Shadowhunters took off down the street, following the trail of light.

It wound through the streets, branching off here and there to rest upon singing and dancing people. They followed it for a good twenty minutes before it stopped very suddenly at what looked to be an abandoned townhouse. The color came back to the world. Jace went and kicked down the door, breaking the boards that had nailed it shut, and they went inside. Clary wondered when she was going to get to kick down some doors.

The inside was dusty and empty. Dim evening sunlight shone through the cracks in the boarded-up window; there was only one piece of furniture in the place, and that was a dusty old armchair on which sat a lady in leather clothing.

"Madonna?" Clary exclaimed.

The woman looked up. She gave them a perfect Madonna smile and stood up. "Oh no, I'm not Madonna. This is simply the form in which I am currently residing. Any musician will do– however, I prefer her over the others."

They drew their weapons. The light from their seraph blades cut strange shadows across the half-lit room– the Madonna-demon looked eerie in the white light.

"Do you really want to kill me?" Madonna said calmly. "All I'm doing is bringing music and joy to the people of New York! Is that such a crime?"

"You made me sing Cosmic Girl," Clary said through her teeth.

Madonna fluttered her eyelashes. "Oh, but, my dear, you were so lovely singing it."

"Somebody kill her," Clary said bluntly.

"Glad to," Alec said grimly, his bow strung and aimed right at Madonna's head.

Madonna smirked. "But can you kill me while you're...dancing?"

The unmistakable intro of Material Girl rose up out of nowhere.

"I hate this song," Isabelle said in revulsion.

"That's too bad," Madonna said gleefully. "You have no choice!"

The four of them started to dance– and Clary had the misfortune of singing the lead part. She figured Alec and Jace were none too happy about their background vocals, and she knew Isabelle was not having fun dancing in the background.

As they sang and danced against their will, Madonna shrieked with mad laughter. Clary saw her eyes glint a luminescent green.

Somewhere in the midst of the chorus Clary shared a glance with Jace.

As soon as the song ended, they'd finish her.

When the song finally faded into silence, Jace pulled two glowing seraph blades from nowhere and flung them through the air. They flashed through the dusty darkness and impaled themselves right into the chest of the Madonna-demon.

She staggered backward.

"No," the demon hissed, showing pointed teeth and a snakelike tongue. She snarled at them, teeth bared. Blood and ichor was quickly spreading across the scaly grey skin of her chest; though the demon still wore the pointed Madonna brazier. Clary felt a deep shudder. That would live on in her nightmares for a while.

"I will be back," the demon hissed. "You have thwarted me for now, Shadowhunters, but I shall be back. And when I am, none shall be safe from my vengeance!"

She was looking right at Jace as she said it. With a last shriek the demon exploded in a pillar of green fire. And then she was gone, leaving only the brazier behind.

A long silence passed.

"We'll burn that when we get home," Isabelle said.