They were in Anna's cell.

"I'm sorry. Elsa won't save you." Ingrid promised.

"You don't know her. You don't know me." Anna retorted.

"But I do. We're a lot alike. We had families, but we both grew up in this palace, isolated and alone. I liked to go to the library and bury myself in a good book. My favorite was an ancient north legend... The Trolden Glass. Perhaps you read it." Ingrid smiled, a cold expression.

"Of course I did. I read everything in there." Anna replied just as coldly.

"Tell me what you remember." Ingrid pressed.

"Giving a book report would be a lot easier if you'd let me go." Anna pointed out.

"The other option is I kill you." Ingrid smiled evilly.

"It's about a north king who had a beautiful daughter he loved dearly." Anna began.

"Go on." Ingrid encouraged.

"He wanted his daughter to be able to see the beauty he saw in her, so he had a mirror made for her birthday. But the day before it, she died, so instead of reflecting her beauty, it reflected the ugliness of his pain and sorrow." Anna finished.

"Very good. What happened then?" Ingrid asked.

"It's been awhile, okay? I don't remember every detail." Anna complained.

"Well, I do. He was so devastated, he decided his kingdom should share his pain. So he spent years harnessing dark magic, used it on the mirror, and cast a spell over his entire kingdom. It made his subjects see only the worst in the ones they loved. And they turned on each other, destroying themselves." Ingrid completed the tale, a catlike smirk on her face.

"What does that story have to do with anything?" Anna asked, annoyed.

"You were in my room. I'm sure you saw the mirror. This is just a small piece of it. I spent years gazing into that mirror, but all I saw reflected back at me was pain, just like the Nordic king." Ingrid sighed, agonized.

"You're going to cast that spell." Anna realized.

"The spell of shattered sight. It would take an entire lifetime to cultivate enough power to cast a spell over an entire kingdom. Luckily I only need to cast it over you." Ingrid grinned and cast the spell on Anna.