Professor Snape: A rather rare herb, gillyweed. Not something found in your everyday garden. Nor is this. [He faces Harry and holds up a small bottle of a clear liquid] Know what it is? Harry: Bubble juice, sir? Professor Snape: Veritaserum. Three drops of this and You-Know-Who himself would spill his darkest secrets. The use of it in a student is, regrettably, forbidden. However, should you ever steal from my personal stores again my hand might just slip over your morning pumpkin juice. Harry: I haven't stolen anything. Professor Snape: Don't lie to me. Gillyweed may be innocuous, but boomslang skin, lacewing flies? You and your little friends are brewing Polyjuice Potion, and believe me I'm going to find out why!

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