Ursula's (Merrin Dungey) crushed soul will be the center of the story in the next episode of "Once Upon a Time" season 4.

Episode 16 titled "Poor Unfortunate Souls," based on the lyrics of one of the most popular songs from the animated film "The Little Mermaid," will center on the mean queen of the ocean. According to spoilers, it will revolve around Ursula's backstory, just before she turned into an evil creature. 

The official synopsis for the upcoming "Once Upon a Time" season 4 episode reads: 

"Hook (Colin O'Donaghue) leverages his complicated history with Ursula to find out what she knows about Gold's (Robert Carlyle) endgame. Gold and the Queens of Darkness torture August (Eion Bailey) for information about the Author as Emma (Jennifer Morrison), Mary Margaret (Ginnifer Goodwin) and David (Josh Dallas) race to find them. Regina (Lana Parilla) grows concerned for Robin Hood's (Sean Maguire) safety while she struggles to maintain her cover with the villains. In a Fairy Tale Land flashback, when a restless young Ursula enlists Hook's help to run away from home, she soon learns it isn't wise to trust a pirate." 

What could have possibly happened between Hook and Ursula that led to their "complicated history?" In one of his earlier interviews as reported by Zap2it, executive producer Eddie Kitsis gave hints on what transpired between the two. 

"It is not sexual. It is, as he said, far worse. When you think about what is worse than having your heart broken -- I would say having your soul crushed," Kitsis said. 

He also said that viewers will see a full flashback of what happened between the two, as well as how Ursula began, as her younger self will be introduced in the episode. 

"Once Upon a Time" season 4 episode 16 is slated to air on Sunday, March 22.