"Lily" is the twentieth episode of the fourth season of the American fantasy drama series Once Upon a Time, which aired on April 26, 2015.When Emma Swan discovers that a former friend from her past, Lily, is Maleficent's long lost daughter, she embarks on a quest to find her and bring her back to Storybrooke in order to reunite her with Maleficent, and Regina teams up with her in a effort to warn Robin Hood about Zelena, but the two are about to face what awaits them outside Storybrooke.