In the closing moments, then, just before the teaser trailer that promised Savitar's true identity would be revealed next week, he revealed himself to Killer Frost -- and what happened next immediately raised our suspicions that Savitar might actually be the returned form of Ronnie Raymond, Caitlin Snow's husband, who died at the end of The Flash season 1.
When Firestorm exploded near the singularity, he managed to close the black hole, but when Firestorm split, Barry only managed to find and save one of the two men who composed Firestorm's matrix: Professor Martin Stein.
That look of surprise and her immediate leap to loyalty seems like the kind of thing that would be nearly impossible to inspire, especially in Killer Frost who, unlike Caitlin, hasn't yet been demonstrated to form personal bonds.
Y'know: the one where they introduced Jax, the guy who bonded with Professor Stein to form Firestorm after Ronnie's death at the end of season 1.
That's my dream: they're fire and ice; they're meant to be together." If Ronnie is Savitar, though, then introducing a former minion of Savitar to inadvertently steal Caitlin's heart and ultimately help her find her way back to humanity would be a particularly ironic way to develop her story -- and it would give the romance that Panabaker suggested maybe her character doesn't need a reason to have existed.