“Once Upon a Time” fans will definitely not want to miss episode 19 of Season 4. Sunday night’s episode, titled “Lily,” will reunite viewers with Emma’s (Jennifer Morrison) old friend from her foster-care days -- who also happens to be Maleficent’s (Kristin Bauer van Straten) long-lost daughter.

According to the synopsis, Emma’s loved ones will begin to panic over the events from episode 18, most notably Cruella De Vil’s (Victoria Smurfit) death. The villain is not a big loss for Storybrooke. However, her death is on Emma’s hands, and that brings her one stop closer to darkness. But Emma’s not worried about her “potential for darkness” because she’s got a new mission to focus on, namely, finding Lily (Agnes Bruckner).

The synopsis reveals Emma will go on a mission to locate Lily and bring her back to Storybrooke after she learns that her “closest friend from her foster-care days” is actually Maleficent’s daughter. The “Savior” will seemingly be trying to right the wrongs of her parents, who are to blame for separating Lily from her mother in the Fairytale Land of the past.

But Emma won’t be alone. She’ll cross the Storybrooke border with Regina (Lana Parrilla), who is venturing outside the magic town on a mission of her own. Last week, viewers discovered that Robin Hood’s (Sean Maguire) wife, Marian (Christie Laing), isn’t who she says she is. With the help of a magical clover from Oz, Regina’s estranged half-sister, Zelena (Rebecca Mader), has been impersonating Marian to ruin Regina’s chance at a happy ending with Robin Hood. Now that Zelena’s secret is out, Robin Hood is in danger and Regina must get to him before it’s too late.

Of course, nothing is ever easy on “Once Upon a Time.” The episode 19 description teases that neither Emma nor Regina will be “prepared for the harsh realities they’ll encounter in the outside world.” But problems also arise in Storybrooke. The synopsis adds that Gold (Robert Carlyle) will face a “crisis involving Belle (Emilie de Ravin).” Finally, “Once Upon a Time” viewers won’t want to miss a flashback to Emma’s childhood. The flashback will give fans a new look at how Emma and Lily met.

“Once Upon a Time” Season 4, episode 19, will be shown on ABC Sunday, April 26, at 8 p.m. EDT.