Parvati pulls me into an alcove on the fourth floor, outside the library. "Padma. I need you to write my History of Magic exam for me," she says. Apparently, this is the sort of thing you can ask of an identical twin and expect to get away with; she's banking on my fidelity. "I know what you're going to say—we both have the exam at the same time. But I've figured out how to get around this tiny inconvenience."
"You want me to write one of your O.W.L.s for you? Are you crazy?"
Parvati glances down the corridor. "Look, I haven't been feeling well. I really, really need your help."
She doesn't look sick to me: maybe a bit anxious, with dark circles under her eyes. Probably from staying up late. "What's really going on?" I say.
"Promise you won't tell a soul? Not Mummy or Daddy, or anyone?" Parvati seizes my hand.
She's my other half, my mirror image. We were inseparable from the time we were conceived until our first night here, after the Sorting Hat pronounced the word Ravenclaw to me, followed by Gryffindor to Parvati, and sent us—with our bags full of books and wands and mice and potions—to different Houses at disparate ends of Hogwarts Castle. I miss her presence every night. Hiding in this alcove, her fingers interlaced with mine, I say to her: "I promise I won't tell."
I already have a hunch what she's up to. She's always been the gregarious twin, planning for both of us; but lately her activities don't always include me. She has Lavender Brown to share secrets with after dark, whereas my only ally is the antiquated Professor Flitwick, head of Ravenclaw, who winks and chirps at me in class as if he knows I need encouragement.
In my first year at Hogwarts, I used to look up potions for self-immolation—not with real fire, but simulated to look authentic. I used to imagine Mummy and Daddy's expressions of horror when I would appear to go up in flames, the bitter smell of ashes, smoke billowing out of the room. Lately, I've considered making polyjuice potion with Parvati's hair, a recipe that would make me look exactly like her, at least for an hour. When you consider our genetics, it's a bit pointless, but I can't help wondering if my reflection would look different in the mirror.
So Parvati tells me what I should have guessed already: about the guy she's dating, that full-of-himself Zacharias Smith,about the subterfuge required to meet him on a certain day, at a certain hour which—as fate would have it—coincides with tomorrow's History of Magic exam. Nothing has changed. I hesitate with my back against the cold stone of the corridor, feeling our dual heartbeats in the grip of my hand. How can I refuse her?