Disclaimer: need I say anything?
As the scene unfolds before his and Ron's eyes, Harry feels like he is watching a horror movie. His and Hermione's Riddle-selves are spitting mean words at his best friend and he hates seeing the redhead flinch at each insult. When the two forms end their speech, they do something Harry should have seen coming, for the locket is acting upon Ron's fears, but he still gasps at the turn of events.
The Riddle forms lock lips and a shiver runs down Harry's spine.
As the kiss goes on, despite his shock, he notices Ron as dumbstruck as he is, except the look on his friend's face is that of sheer despair. The boy averts his eyes back to the locket and can't help noticing how his Riddle version touches the girl intimately, seductively, while their mouths are sealed in a passionate, lustful kiss that makes Harry suddenly feel a heat spread within him. He perceives with a hint of desire the way Riddle-Hermione grabs a handful of her lover's hair and pulls him closer, closing any gap between them that could have gone unnoticed. The hand that is resting on the girl's hip reaches incredibly close to her breast and Harry finds himself wishing it went further up just a little.
A sound coming from Ron's way makes him snap back to reality and he watches the redhead slay the locket with a rage scream of "no!", making the two forms fade immediately in the thin air. As Harry sits there with a quickened breath and a fast-pounding heart, his mind keeps replaying what he just saw, each time making him more and more anxious. Somewhere in his head, a voice that sounds a lot like Hermione's starts saying his name in a voluptuous plea.
Although he assures Ron his feelings for Hermione are those of a brother when asked about them, Harry hears a growing part of his mind whisper…
"What if?"