Once Upon a Time is going to the Underworld to try and save Captain Hook's (Colin O'Donoghue) soul from the afterlife. One would think that the team had earned an arc at home in Storybrooke after spending so long in Camelot during the first half of the season, but there's no rest for true love.
The show has featured multiple trips to magical lands abroad, starting with a journey to Neverland at the beginning of Season 3, and each sojourn has been carried out with varying degrees of success. Neverland seemed to drag on too long and lacked focus. (Was it about rescuing Henry (Jared Gilmore), Rumple's (Robert Carlyle) battle with his father, or Emma's (Jennifer Morrison) abandonment issues?) Camelot attempted to get everyone involved to make up for seasons of under-using fan-favorite characters, but inevitably overcrowded a story line that should have focused on only one person. Both trips took away from Storybrooke, which in a way is also a central character of the story.
There's a lot of potential for the Underworld — starting with the fact that it's a twisted version of Storybrooke instead of a completely different place — but there are a few things the show could do to make sure the group gets the most out of their new surroundings.
1. Keep everyone on mission
The mission in the Underworld is to get Hook back to the land of the living. The heroes will obviously have to face challenges in doing that, otherwise everyone would be getting their loved ones back from the dead all the time. Those challenges should affect the heroes in different ways, but if the "unfinished business" of the Underworld distracts everyone into their own subplots, then it loses the pace of action needed to keep the storyline interesting.
2. Use familiar faces to strengthen character, not plot
This is tangentially related to number one, but the intriguing thing about the Underworld is getting to see faces we thought we'd lost forever. However, those familiar faces would be best served if they help the core group of heroes tie up their own unfinished business rather than opening new cans of worms.
Cruella de Vil (Victoria Smurfit) is one of the most highly-anticipated returns of the season, and will no doubt force Emma to deal with the darkness she possessed long before she became Dark Swan. Hopefully that resolution leads to Emma the place she needs to be in emotionally to split her heart and save Hook (because no one wants a heart with a dark spot).
3. Let new faces stand on their own
In previous Once story arcs, the big bad of the season inevitably has a secret past with one of the core heroes. Making that work requires creating flashbacks that thread the new villain into an already elaborately-woven back story. The side effect is that fans have to relive things they've already had drilled into them about the pre-curse Enchanted Forest.
Hades (Greg Germann) will be the ultimate foe of the Underworld, and Once could save themselves a lot of time and energy if this is the first time any of the heroes have ever encountered him. Not meeting him in a previous life also will make his powers and tricks more surprising and fun for the audience.
Once Upon a Time returns Sunday at 8/7c on ABC.