When Professor McGonagall calls her, she's scared to the bone. Her greatest fear is being reprimanded by her Transfiguration teacher, and as she walks to her office, she mentally rewinds everything she did the previous term, sifting through to check for any mistake she might have made, any wrong thing she might have done without knowing. She doesn't come up with much.
They reach the office. She's offered a biscuit, which she refuses, because her stomach is churning with anxiety. But then her teacher explains the situation: she's taking too many subjects, and if she's still absolutely sure she wants to take them all, the only way is to use a Time-Turner. She's read about them, but it's still half a dream to be allowed to have one. So she listens, half in a trance, as its rules are explained to her. She knows it is equipped with a charm that will take her back past five hours, and that it's impossibly difficult to get hold of one.
Her professor stops and looks her in the eye. "Please use it only for your classes," she says, placing the delicate hourglass in Hermione's hand. "The Ministry doesn't give out one of these easily. I had to specify that you are a model student, reliable, a person who could be trusted to use it only for its purpose."
"Yes, Professor," she says.
She frowns; her voice gets quieter. "It is easy to say yes now, when there is no temptation, but you must never use it for the wrong purposes," her teacher says. "It has ruined many lives before you. You are a smart girl; you must understand the allure the power to alter time could have to many people. Please use it wisely."
She nods, fastening the delicate clasp around her neck. She looks at the fragile glass for a moment. For such a tiny thing to have the power to change time was frighteningly remarkable.
She tucks the hourglass down the front of her robes, thanks her professor, and heads off to the Great Hall.
Her first class requires the use of the Time-Turner: Divination and Study of Ancient Runes. She doesn't have a very high opinion of the former, and Professor McGonagall made it clear that she didn't think Divination was a subject worth using a Time-Turner on, so she decides to do that first so she'll have her mind clear for Runes.
The class is worse than she expected. She'd pretty sure the so-called teacher is a fraud: most of her predictions don't seem rooted in any scientific or magical method, nor does she have any explanation for why things happened except that they just happened. She runs out of the stifling room as soon as the class was over, putting her book into her newly-mended bag and making sure she's out of sight before turning the hourglass carefully.
It feels better than travelling by Floo, but a bit stranger, watching the blurs of colour and sound around her as the world moves one hour back in time. She waits till it stops before making her way to Runes.
When she's sitting in the dormitory that night, a commotion arises over Lavender losing a watch she'd kept on her bed. She says it was there an hour ago before she went down for dinner, and has to be escorted to the common room, where Parvati desperately tries to calm her down with little success.
She feels uncomfortable. One twist of her Time-Turner and she could find out what happened to it. Her hand reaches up to the hourglass and she resists the temptation with the greatest difficulty.
She now understands why the Ministry would be so worried. If she, a normally disciplined person, can't control herself, what would the world be like if someone else got hold of it?
That rather disturbing thought rolls in her head as she falls asleep.