Captain Hook teamed up with Ariel to track down a common enemy on the latest episode of "Once Upon a Time."

In "The Jolly Roger," Hook (Colin O' Donoghue) and his men take a carriage hostage and split the loot. Later, after copious amounts of drinking, he gets a blow to the head from an angry Ariel (JoAnna Garcia Swisher).

In Storybrooke nine months later, Regina (Lana Parrilla) conjures up a protection spell for David (Josh Dallas) and Mary Margaret's (Ginnifer Goodwin) apartment.

Back in the Fairytale Land That Was, Ariel accuses Hook of kidnapping her prince. But it turns out that Hook didn't kidnap him--Blackbeard did. The two then decide to track down Blackbeard.

Meanwhile, Regina begins teaching Emma (Jennifer Morrison) magic lessons, and Emma's magic skills prove to be quite powerful.

In Storybrooke, Ariel washes ashore after searching everywhere for Prince Eric. Hook recognizes the cloak Eric wore during the past year and Belle (Emile de Ravin) sets a tracking spell on it. The cloak brings Hook and Ariel to the docks, where it disappears into the waters, revealing that the prince had an unfortunate fate.

Back in Fairytale Land, Ariel and Hook find Blackbeard and the stolen Jolly Roger. Blackbeard gives Hook an ultimatum: Hook must admit that he has "gone soft," and surrender the ship to save Eric, or he tosses Blackbeard overboard and Prince Eric dies. Hook takes his ship back, and Ariel angrily goes off in search of Eric.

In the present, Hook runs after Ariel and confesses his selfishness. Then Zelena (Rebecca Mader) appears, admitting that the whole thing was a ruse. She says that Ariel and Prince Eric are actually living on an island together in another realm.

Zelena tells Hook to kiss Emma, which will make all of her powers disappear forever. If he refuses, she will take the lives of everyone, one by one.

Regina challenges Emma to use mirror magic to look between realms. Emma sees that Hook is telling the truth about Ariel and Eric living happily every after.

Hook then goes into town to confront Zelena.

On the next episode, "Bleeding Through," "After Zelena steals Regina's heart, Regina casts a spell so that she can speak across the realms to her dead mother, Cora, to discover the truth about why she abandoned Zelena, and Belle stumbles across what Zelena's ultimate endgame is. Meanwhile, in the Fairy Tale Land that was, young Cora is duped by a man claiming to be a prince and finds herself alone and pregnant. But a chance meeting with a real prince could lead Cora to the royal life she's always craved, but she must keep her pregnancy a secret or risk losing everything."

Watch the promo for "Bleeding Through" below, which airs Sunday, April 20 at 8 p.m. EDT on ABC.