The winter finale of "Once Upon a Time" season 5 airs tonight. Titled "Swan Song," the tables have turned as Dark Hook is now the one set to bring terror in Storybrooke, with the entire group of past dark ones ready to see innocent blood pour and destroy light magic for good.

In a trailer for the upcoming installment, Hook's revenge scheme is complete and all that's needed is to carry it out and watch it come to fruition. To give an idea of the horrors to come, Hook warns Emma "You get to watch everyone you love die."

Although trembling with fear, Emma responses "I will protect my family, even if I have to kill you to do it." At that moment, the "Once Upon a Time" season 5 promo cut to a scene where the Dark Swan appeared to have stabbed her once beloved and noble lover.

Emma feels responsible for putting everyone in great peril, which is why she won't stop until she irons out this big mess even though Rumple makes it sound like the only thing left to do is spend their remaining hours with their loved ones before they all perish.

In the "Once Upon aTime" season 5 midseason finale, the Dark Swan instead opts to use the time left to stop the atrociousness that is bound to happen that will lengthen her moments she get to be with her loved ones by stopping Dark Hook once and for all.

Of course, this puts her in a tight spot as Hook was once the man she loved so dearly. Will she be able to bring Hook back to the way he was or resort to slaying him for everyone's good? In their ultimate standoff, the synopsis teases that "Hook's actions will devastate Emma in a way no one saw coming."

Meanwhile, the upcoming "Once Upon a Time" season 5 episode will also feature a flashback to Fairy Tale Land. To learn if Hook is capable of obliterating a demon from her past, the Evil Queen puts his courage to the test by having him meet head-on one of his own. A sneak peek for this scene can be seen here.

The midseason finale of "Once Upon A Time" season 5 "Swan Song" airs tonight, Dec. 6 at 8 p.m. ET on ABC.