Operation Mongoose Part 1

"Episode 421" is the twenty-first episode of Season Four of ABC's Once Upon a Time. It will be the eighty-seventh episode of the series overall, and will premiere on May 10, 2015.

Starring

 * Jennifer Morrison as Emma Swan
 * Lana Parrilla as Evil Queen/Regina Mills

Guest Starring

 * Sean Maguire as Robin Hood/Robin Hood