They must get away from Malfoy and his lackeys

They try to

They pelted down the corridor, the sound of mocking laughter and misfired spells echoing behind them. Someone’s arm shot back and accidentally flicked past Ginnys mound making her squeak in pleasure and moisten a little bit more “Eeeeek!” she squealed, her face turning beetroot.

They burst onto the landing of the Grand Staircase, a massive, multi-level construction of moving staircases crowded with students. The sudden appearance of a naked Ginny caused a wave of gasps and pointing fingers.

"Locomotor Mortis!" Malfoy's voice shouted. The spell, meant for Ron, missed and hit the very staircase Ginny was trying to ascend. The jolt of magic caused the stone steps to momentarily liquefy, turning into a thick, gooey tar. Ginny's bare feet sank into it, trapping her fast. Harry, right behind her, crashed into her, his full body pressing against her back to stop himself from falling. His chest was flush against her, his arms wrapping instinctively low around her waist to steady her. For a moment, his hands drifted across her soft mound, and she could feel the hard press of his rigid member against her bare ass. A hot, confusing jolt shot through her, a mixture of shame and a traitorous thrill. He quickly pulled back, his face flushed, but the feel of her skin was burned into her mind.

"Finite!" Harry cast, freeing the last of the steps. Ron grabbed Ginny's arm, his grip tight, and they scrambled down the stairs, her legs still coated in the sticky tar.

"Split up!" Harry commanded. "Ron, take her to the third-floor corridor! I'll lead them away!"