Seems a bit strange that Quirrell didn't ask Harry to confirm in Parseltongue that Harry didn't have any contingency measures beyond those Quirrell already knows about (Lesath under the cloak). In the last chapter's discussion there were theories that Cedric Diggory might be around, time-turned with Harry. Even if not, why wouldn't Q make sure H doesn't have anyone else around to help or set up any other measures? Harry's promise "shall call for no help" isn't enough, if things are already set in motion for someone to help him.

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