Hermione and Ron are very confused and don't understand why Ivan trusts Snape so much.
Harry was even more hesitant, and he doubted that Snape had another important reason, that is, when the other party taught him brain sealing, he always wanted to know what the headmaster had left him.
But when he thought of that will, Professor Dumbledore allowed himself to trust Snape when necessary, and Harry swallowed his words again, because he could not be sure whether Snape was working for Voldemort or lurking around Voldemort to provide information for them.
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