A deleted scene from the final Harry Potter film can be found as a bonus feature on its Blu-ray incarnation. In the scene, dubbed "The Goblins of Gringotts," we see the characters played by Daniel Radcliffe, Emma Watsonand Rupert Grint plotting to break into Bellatrix's vault in the Gringotts Wizarding Bank.
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Watson's Hermoine Granger at one point holds up a strand of hair belonging to the witch, played by Helena Bonham Carter....then Harry asks, "You're sure that's hers?".....Hermoine says, "Positive." Then Ron says, "How will we know what it is when we get in there?"