The Storybrooke heroes may have successfully returned to their own town after spending time in the Underworld, but things are not looking good for everyone in the upcoming episode of "Once Upon a Time" season 5.

In the episode called "Last Rites," Emma (Jennifer Morrison) will seek the help pf Rumplestiltskin (Robert Carlyle), Robin (Sean Maguire), Henry (Jared S. Gilmore), and Regina (Lana Parrilla) to stop Hades (Greg Germann).

However, the trailer for the episode warns that the battle between the heroes and the lord of the Underworld will not have a happy ending. "The King of the Underworld enters our world, igniting a devastating conflict that someone will not survive, breaking the very heart of Storybrooke forever," the voice-over teased.

Toward the end of the trailer, the residents of Storybrooke are seen mourning the death of a still-undisclosed character at a funeral. Since both Emma and Regina's faces are featured in the trailer, it means that the two survived the fight against Hades. But who is the one in the casket?

The official synopsis for the episode reads:

"Emma, David, Regina, Robin and Henry are finally back home in Storybrooke and reunited with Snow, but, unfortunately, they still have to contend with Hades, who continues to deceive Zelena as he lays out his plan to use the all-powerful Olympian Crystal to take over the town. The heroes desperately search for a way to defeat Hades while Hook does the same in the Underworld, looking for those missing storybook pages. Regina and Robin take a more direct approach, which culminates in an epic showdown that will leave our heroes forever changed."

How will Emma deal with another grief after the love of her life Hook (Colin O'Donoghue) died in the previous episode, titled "Firebird?"

"Once Upon a Time" season 5 episode 21 airs on Sunday, May 8, on ABC.