"Mother" is the twenty-first episode of the fourth season of the American fantasy drama series Once Upon a Time, which aired on May 3, 2015.In this episode, Emma Swan reunites Lily with Maleficent, Isaac must find a new ally as Gold's heart grows darker, and Regina and Robin Hood must deal with Zelena's pregnancy. Back in the Enchanted Forest, Regina is reunited with Cora upon her return from Wonderland, but questions her mother's intentions as to why she wants to help her.