This might, in fact, be a suicidal mission. You didn't have to be at camp long to learn how dangerous Mr. D was. But he seemed so uncaring about most things so maybe he wouldn't notice or care and Hermione had never been personally subjected to his bad side so she wasn't scared enough of him. Also, she was fairly used to getting into trouble and talking her way out of it. She didn't want to get Paul in trouble, but she also didn't think it would be too big of a deal. And finally, she just couldn't help it. She was a child of Hermes doing what Hermes kids did! Once she got a mischievous idea in her head, it was nearly impossible to avoid carrying it out, no matter how stupid. And now, even though this had started because of Paul, she was dying to get up there and go through the relics. 

When the two camp guardians left, Hermione sighed with relief. Then she looked at Paul and smiled. "Don't worry, this'll be awesome." She thought about grabbing his hand and running toward the back door but luckily suppressed the impulse. And instead of running she just glided forward casually and went right up to the back door like she had every right to be there. She tried the door and found it was locked. Hermione paused. Then, instead of fiddling with it she turned and stepped aside. "Okay, man of the hour. Most Hermes kids can magically pick locks. Give it a try." This was, after all, supposed to help test his abilities.

She tried to smile encouragingly but only managed a kind of grimace. She SO did not want to be related to him. And that's what it would most likely mean if he did unlock this door. "Hermes..." she murmured, pleadingly. Thinking: 'tell me he's NOT your son pleaseeee.'