Yeah. This was a good one. Very solid, very moving... perhaps somewhat redundant and even a little shallow? On a level of personal enjoyment, I'm all smiles over here. But on a more critical note, I wouldn't call this episode flawless.
Cons:
What do I mean exactly? Well, let's take a look at the main story of the night. In flashback, we learn that Killian and Liam were slaves aboard a ship for a long time, and they worked hard to earn enough money to buy their freedom. On the eve of getting commissions to join the navy, Killian gets drunk and gambles away his savings. Liam refuses to leave his brother behind, and the two continue in servitude. Eventually, Liam and Killian commit a mutiny to save the rest of the crew from the greed of the captain, who wanted to sail into a storm in search of a mythical gem. The plan is to turn around and run from the danger, but Hades shows up to make a deal with Liam: let the men aboard the ship die, so that he, Hades, can have fresh souls. In exchange, Hades will spare Liam and Killian's lives, and also give Liam the gem, thus ensuring he can get a commission in His Majesty's Navy. Liam takes the deal, and Killian never finds out, believing his brother to be a hero who tried his hardest to save all the men.
In the Underworld years later, the gang believes they can find out more about Hades and how to destroy him if they have the Underworld equivalent of the Story Book. They find it using information Henry found out about (I'll get there later). But Liam first gets a visit from Hades, who threatens to tell Killian the truth unless Liam tears out all the pages about Hades. Liam finds the book and destroys the pages, but Emma discovers him, and eventually Killian realizes his brother has been lying to him. The men who died aboard the ship all those years ago show up for their revenge, and Liam sacrifices himself for Killian and the others. His act of sacrifice completes his unfinished business, as he has finally made amends for his past wrongdoings. He and the other sailors all get to move on, while Killian stays behind. His unfinished business won't be finished until he and the others find a way to defeat Hades.