Finally reunited, Hook and Emma must find a way to defeat Hades so that they can return to Storybrooke with Snow, David, Regina, Robin, Henry and Gold. A surprise visit from Hook’s departed brother Liam just might provide the lead they were looking for — others who have tried to overthrow Hades spoke of a book that contained the key to his downfall. Tired of watching from the sidelines, Henry secretly takes matters into his own hands while the others search for the book. Meanwhile, Hades redoubles his efforts to trap the heroes in the Underworld by playing them against one another. In flashbacks, the bond between the two young Jones brothers is tested and strengthened on a merchant ship heading into a dangerous storm.