ABC teased "Once Upon a Time" fans about the show's upcoming 100th episode with photos that take you down on a stroll down memory lane.

Now on its fifth season, ABC's fairy tale based TV series is set to bring the show's protagonists on a journey to the Underworld to save one of their comrades: Hook (Colin O'Donoghue).

In the 100th episode that also acts as the series' winter premiere, Emma (Jennifer Morrison), Snow (Ginnifer Goodwin), Charming (Josh Dallas), Robin (Sean Maguire), Regina (Lana Parrilla), Henry (Jared Gilmore), and Gold (Robert Carlyle) arrive in the Underworld only to find that they will not accomplish their goal that easily.

Titled "Souls of the Departed," the episode is said to feature souls that have unfinished business with the living.

 The #OUAT heroes make it to the Underworld but does everyone return to Storybrooke?

A photo posted by onceabcofficial (@onceabcofficial) on Feb 17, 2016 at 4:48pm PST

With that said, stills from the episode show both happy and not-so-happy reunions between parent and child -- Regina with her mother Cora (Barbara Hershey) and Gold with his father, Peter Pan (Robbie Kay).

As it turns out, Cora, who had never been cordial with her daughter per co-creator Eddy Kitsis, has become the "mayor" of the Underworld version of Storybrooke.

As is expected, the "Once Upon a Time's" winter premiere will pick up from season 5's winter finale episode titled the "Swan Song."

For those who were unable to watch the episode, the "Swan Song" saw a forthcoming dark siege in Storybrooke. The Dark Ones pursue the living to use as a sacrifice to pave the way for their resurrection to the realm of the living.

"With doom imminent, Gold advises Mary Margaret, David and the rest of the heroes to spend their last fleeting moments enjoying the company of their loved ones. Emma, however, refuses to give up, knowing that she is responsible for righting all the poor choices she made as Dark One -- there's only one problem, Dark Hook," the episode's official recap stated.

Once in Hades' domain, the heroes encounter souls that are both good and evil -- the latter mainly comprised of souls with personal vendettas against some of them.

Aside from these exciting turn of events, showrunners also promise a celebration of sorts to commemorate the show's 100th episode.

Apparently, someone from the Evil Queen's past has come back to give Regina the perfect birthday gift.

Who that character is, exactly, remains a mystery. It can only be answered when the episode airs on Sunday, March 6 on ABC.