ONCE UPON A TIME will go on an undersea adventure in “Dark Waters”!

Get ready for a high stakes Hook-centric episode of Once Upon A Time!

Faran Tahir joins the show as Captain Nemo of 20,000 Leagues Under The Sea fame, who is shaking things up for Hook with a new mission. Take a look!

While the Nemo story is thrilling in itself, two new clips are showing us what the episode will really be about: family dynamics.

First, we see Henry having an interesting meeting with The Evil Queen all about Hook and his place in the family. Of course, the queen has some ulterior motives and works to turn Henry against the others.

This lengthy clip gives the backstory on Captain Nemo, explains how he came to find Hook, and introduces a special mission that Killian must complete to fix his own wayward soul. This is all a flashback, of course, which will put the present in an interesting perspective!

Well, Hook might have much in terms of biological family, but we still have a feeling that his adopted family of sorts will trump all!

“Dark Waters” airs tonight on ABC.

Emma tries to convince Aladdin to work with Jasmine to help Agrabah, while Regina teams up with Snow and David to free Archie from Zelena. The Evil Queen sows suspicion between Henry and Hook, even as Mr. Gold reminds her of his most important lesson. Meanwhile, in the past, Hook finds himself kidnapped by the mysterious Captain Nemo and held captive inside his legendary submarine, the Nautilus.