Harry thinks about the things he shouldn't know as he walks down the stairs to the common room.
At the bottom of the stairs, he sees Hermione standing in front of the still lit fire with a dark red rose with gold leaves.
He doesn't say anything as she whispers a spell to vanish it.
Later in Transfiguration, he sees Hermione smiling.
He looks around the room to see what it was that made his friend smile like that.
As he looks over McGonagall's desk, he sees her twirl a dark red rose with gold leaves in her hand.