Hook (Colin O'Donoghue) will meet the enigmatic captain of the famous Nautilus in the upcoming episode of "Once Upon a Time."

In the episode titled "Dark Waters," the promo shows that the pirate will be immersed in the exciting world of Jules Verne's "20,000 Leagues Under the Sea." It has been previously revealed that the ABC series has tapped Faran Tahir to play the iconic role of Captain Nemo, the tough leader of the Nautilus submarine. In the teaser, Hook is revealed to have been captured and brought inside the sub. When he opens his eyes, Nemo's people are surrounding him. In classic Hook fashion, he overpowers them and checks where he is. Nemo then appears, telling Hook that he has a mission for him.

It remains unclear how the pirate and the captain's storylines are intertwined. Executive producers Adam Horowitz and Edward Kitsis previously told Entertainment Weekly that they were planning an exciting plot for the two characters. Nemo's escapade in the Nautilus was the topic of Verne's classic 1870 novel. It will be interesting to see why he needs Hook's help in something. The pirate has no choice but to assist, of course, since he cannot just escape from the submarine without drowning. Hook is literally Nemo's prisoner. If he performs well in the mission, perhaps, the captain will let him go.

"We're thrilled to give a Once Upon a Time spin to the classic character of Captain Nemo from one of our favorite Disney films, 20,000 Leagues Under the Sea. We're excited to see his mythology merge with Storybrooke's own captain — Hook [Colin O'Donohue]. If for no other reason than to see the Jolly Roger go up against a submarine," the EPs shared, according to EW. 

"Once Upon a Time" season 6 airs on Sundays, 8 p.m. ET on ABC.