At Sony's E3 2014 press conference, it was revealed that a standalone piece of downloadable content for Infamous: Second Son, called First Light, is coming in August. The trailer indicated that you play as Fetch, a character from Second Son who has neon-based powers. The brief trailer showed Fetch being tormented by voices, as well as doing a bit of running around, zapping, and pouncing, leaving her signature laserlike lines in her wake.
You won't need to own Second Son to play First Light, though if you do, you'll get access to additional content. We'll bring you more on First Light as it becomes available.