Voldemort's taken over, and everyone Hermione cares about is dead. So she uses a time turner and goes back to the start, to teach Tom Riddle to love, as he helps her cope with the loss of those who he would kill. Irony, trust issues, and new emotions.
It took a day or two to adjust to a world in Flashback Grayscale™, but that was the least of Hermione's worries. Fortunately, Hogwarts was much the same as in her own time. She searched the usual student haunts each day and finally found Tom Riddle torturing small furry animals by the lake.
"Tom Riddle?" she asked, annoying the readers by repeating the name when it had just been stated in the narrative.
"What do you want?" he replied without looking up from the shrew he was marring.
Hermione took a deep breath. "In the future, you kill everyone I care about! I have come back in time to teach you to love! There shall be Irony, Trust Issues, and New Emotions! I love you, Tom Riddle!" As the readers cringed at the abuses heaped upon the poor exclamation mark, she leapt at the future Dark Lord. Or the past Dark Lord, depending on one's perspective. He couldn't be the present Dark Lord, even in the sense of being present, because he wasn't the Dark Lord just then.
The paradox inherent in the last three lines (and indeed the entire situation) decided to look the other way. Tom already had his wand out and wasted no time at all in dispatching the creature masquerading as Hermione Granger. He shook his head in clinical disbelief.
"When will they learn I'm incapable of normal human emotion? I'm a bloody psychopath. Even a Muggle could see that."
The PPC agent assigned to take care of the Sue shrugged. "The world may never know. Now, if you'll look this way, please, it's standard procedure...."