Board Thread:Spoilers!/@comment-1916997-20151229033119/@comment-1916997-20160113061709

http://tvline.com/gallery/tv-spoilers-2016-season-premieres-photos/#!14/once-upon-time-underworld/

Well, if 518 is the Ruby and Mulan episode, then I'm guessing 517 is the Belle episode, and 519, 520, or 521 is the Robin episode.