Plot summary
As everyone returns to Storybrooke, they plan to stop Hades, who wants to unleash the Olympian Crystal on those whom he sees as a threat. When Zelena's feelings blind her to the truth, Emma, Regina, and Robin have to find a way to prove Hades's deception, leading to Robin sacrificing his life for Regina and Zelena using the Crystal to destroy Hades. In the Underworld, a deceased Arthur, killed by Hades in Storybrooke, joins Hook in finding the missing element in killing Hades. After he succeeds in reaching Emma, Hook is allowed to move on but is revived by Zeus, while Arthur stays behind to fulfill his destiny of repairing a "broken kingdom".
Zelena names her daughter Robin in honor of her father during his funeral. Meanwhile, after Moe refused to help bring Belle back from her sleeping curse and Hades chose not to cut a deal, Gold takes advantage of the situation by acquiring a piece of the Crystal for a new plan.
Credits
Adapted from Wikipedia contributors, Once Upon a Time season 5. HTML formatting and reference markers removed.