Once Upon a Time 5×18 “Ruby Slippers” – In flashbacks, Ruby and Mulan find themselves in Oz, where they meet Dorothy. After the three witness Zelena’s return to Oz, they look for a way to defeat her once and for all. However, Dorothy mysteriously disappears, and Ruby’s search for her new friend lands her in the Underworld. Reunited with the heroes, Ruby teams up with Emma, Regina and Snow to continue looking for Dorothy. Meanwhile, Snow and David struggle with not being able to be with their son, Neal, and devise a plan so that one of them can escape the Underworld, on “Once Upon a Time,” Sunday, April 17th on ABC.