This season of Below Deck features Captain Lex Luthor trying to keep guests happy and the crew in line. Bosun Batman is frustrated that chief stewardess Wonder Woman keeps asking him to help entertain the guests. 2nd Steward Harley Quinn tries to keep Chef Joker focused and on task so meal service is delivered on time.

As the crew takes a break, tensions rise when Lex Luthor accuses the Joker of sabotaging the ship's kitchen, leading to a heated argument between the two.

As the crew works together to fix the kitchen, Batman and Wonder Woman grow closer, but their budding romance is threatened when the Joker reveals a shocking secret from Batman's past.

As Wonder Woman confronts Batman about not telling her about previously being engaged, Lex Luthor meets with Chef Joker to discuss an upcoming guest meal and explains that it needs to have a big surprise. Meanwhile, Harley starts planning an excursion for the guests by herself and is frustrated that Wonder Woman is distracted by Batman.

As the crew prepares for the big guest meal, Harley Quinn's excursion plan goes awry when she accidentally books a pirate-themed party for a group of senior citizens, causing chaos and confusion.

As the pirate-themed party gets underway, Lex Luthor's annoyance turns to outrage when he discovers that the Joker has replaced the planned meal with a ridiculous "Joker's Wild" menu featuring dishes like "Laughing Gas Lasagna" and "Joker's Juice Jambalaya".

As the guests arrive for the pirate-themed party, Lex Luthor's attempts to salvage the evening are thwarted when the Joker's "Laughing Gas Lasagna" is served, causing chaos and hilarity among the senior citizens.

As the laughing gas wears off and the senior citizens return to normal, Lex Luthor demands that the Joker be fired, but Wonder Woman intervenes, suggesting a compromise that will keep the Joker on board.

As the party comes to a close, Wonder Woman and Batman share a moment of tender intimacy, while the Joker and Harley Quinn look on with amusement, and Lex Luthor seethes with resentment.

As the night winds down, Lex Luthor confronts Wonder Woman about her growing relationship with Batman, warning her that it will only lead to trouble and compromise her judgment. Wonder Woman tells Batman she needs to keep her distance and focus on work.

Having been pushed away by Wonder Woman, Batman confides in Harley Quinn at night. They share a few drinks and end up in the hot tub together.

The next morning Wonder Woman confronts a hungover Batman about his hooking up with Harley Quinn the night before in one of the guest suites. Joker congratulates Harley Quinn on the hook-up Lex grows frustrated with all the drama on board, the dirty hot tub and lack of preparation for the next group of guests

As the tension between Wonder Woman and Batman reaches a boiling point, Lex Luthor tries to intervene, but the Joker's constant meddling and Harley Quinn's playful teasing only add to the chaos.

As the ship prepares to dock, Lex Luthor announces that the next group of guests will be a high-profile tech conference, and he expects everyone to be on their best behavior, but the Joker has other plans.

As the tech conference guests arrive on board, Lex greets the guests. Meanwhile Chef Joker is preparing appetizers with some extra spice. Wonder Woman and Batman suspect Chef Joker is up to something and taste the appetizers before they are served. They prevent the spiked appetizers from being served and Lex finding out.

Lex tries to keep the guests happy while announcing they are setting course for an unexpected destination. Batman and Wonder Woman work together to hide Chef Joker's antics from Lex so that he doesn't get fired, while Harley Quinn teases of Batman about steamy hookup.

As the ship approaches its new destination, Lex Luthor reveals that it's a private island where the guests will participate in a high-stakes tech competition, but the Joker has other plans, and Batman and Wonder Woman must work together to stop him.

As the tech competition wraps up, Batman and Wonder Woman reassure Lex that everything will be ok, are skeptical to eachother that he can pull it off. Chef Joker reveals his big surprise to the crew, an elaborate 21 course meal with wine pairings for the guests.

As the guests sit down to enjoy the Joker's elaborate meal, Batman and Wonder Woman are on high alert, expecting something to go wrong, while Lex Luthor is confident that the evening will be a success.

Lex informs Batman and Wonder Woman that the guests are loving the food, while Batman, Wonder Woman and Harley struggle to keep up with service.

As the evening winds down, Lex Luthor thanks the crew for a successful dinner service, but Batman and Wonder Woman are still on high alert, expecting the Joker to pull one final trick. He reveals that the trick was that there was no trick after all.

As the guests depart and the crew begins to clean up, Lex Luthor reveals that he has received a glowing review from the tech conference organizer, and the crew is rewarded with a well-deserved break.

As the crew enjoys their break, Wonder Woman and Batman share a moment of tender intimacy, while the Joker and Harley Quinn look on with amusement. Joker suggests that Harley is jealous of Wonder Woman. Harley tries to deny it but Joker realizes she is.

Harley confides in Wonder Woman that she can't get her and Batman out of her head. She realizes she likes them both. Wonder Woman kisses Harley, then invites her to join her with Batman in the guest chamber. Joker and Lex are shocked and amused and the new throuple.

As the throuple's relationship becomes more public, the Joker's antics become more erratic, causing Lex Luthor to worry about the impact on the ship's reputation, while Harley Quinn struggles to balance her feelings for both Wonder Woman and Batman.

As the throuple's relationship continues to blossom, Lex Luthor tries to capitalize on the ship's newfound notoriety by hosting a "Love Boat" themed cruise. Batman confronts Lex about trying to profit off his complex relationship. The Joker tells Batman he should have expected consequences

As the "Love Boat" themed cruise sets sail, Batman's discomfort grows as he's forced to participate in cheesy couples' activities with Wonder Woman and Harley Quinn, while the Joker provides a play-by-play commentary of the proceedings.

As the "Love Boat" cruise comes to a close, Batman, Wonder Woman, and Harley Quinn share a romantic dinner together, while the Joker and Lex Luthor look on, each with their own agenda.

As the ship returns to port, Lex Luthor reveals that the "Love Boat" cruise was a huge success, and he's already planning a sequel. Batman reluctantly ask Joker for advice on how to make Harley happier, given Harley and Joker's prior relationship. The Joker gives Batman bad advice.

Batman takes the Joker's advice and buys Harley a giant mallet, which she uses to smash up the ship's galley, causing chaos and destruction, while the Joker looks on, laughing maniacally.

As the crew tries to clean up the mess, Lex Luthor berates Batman for his poor decision-making, while the Joker continues to laugh and Harley Quinn looks on, still holding her giant mallet.

As the crew finishes cleaning up the mess, Harley tells Wonder Woman she is disappointed in herself that she got Batman in trouble with Captain Lex. She asks Wonder Woman what she can do to make it up to Batman. Wonder Woman gives her some helpful and sexy advice.

Harley Quinn sets up a romantic dinner for Batman, complete with candles, flowers, and a seductive outfit. harley tells Batman how much she cares about him, and wants to be together forever. Then Harley reveals her other surprise, Wonder Woman in a matching seductive outfit. But just as things are getting intimate, the Joker bursts in, laughing maniacally and ruining the moment.

As the Joker continues to laugh and cause chaos, Lex Luthor steps in to try and restore order, but ends up getting caught up in the mayhem, while Batman, Wonder Woman, and Harley Quinn try to salvage what's left of their romantic evening.

As the chaos dies down, Batman, Wonder Woman, and Harley Quinn share a laugh and a romantic moment, while Lex Luthor storms off, fed up with the Joker's antics, and the Joker looks on, a hint of sadness in his eyes.

As the night comes to a close, Batman asks Wonder Woman and Harley Quinn to be his partners in a throuple relationship. They agree, kiss and decide to go to the guest suite together while the Joker looks on, a mix of sadness and longing in his eyes as he realizes he does not have anyone that adores him anymore like Harley used to. Lex Luthor watches from the shadows, a calculating glint in his eye as he plots how he can profit from the throuple.

As the throuple's relationship becomes more public, Lex Luthor starts to capitalize on their fame, selling merchandise and promoting their love story, while the Joker becomes increasingly isolated and withdrawn, feeling left out and alone.