Joss isn’t sweating for the wedding, she’s learning how to fight back. That’s how episode 2 of ABC’s “Mistresses” begins — with Joss sparring against a woman in her self-defense class who is much more advanced than she. The teeth-gritting Season 4 scene of the two brawling then explains the extreme bruising hidden under her clothes.

“Woah, what happened here?” Harry (Brett Tucker) says when he sees the purple marks on his fiance’s arm. But Joss (Jess Macallan) assures him it looks way worse than it actually is. As they start stripping off more clothing, their steamy moment gets disrupted by the sound of the doorbell. It’s Kate (Tabrett Bethell), Harry’s sister, whose smile quickly fades when she sees Joss’ shirt unbuttoned.

“We were doing laundry,” Joss lies after Kate asks if she was interrupting “something.”

As Joss quickly tries to button her blouse, Karen (Yunjin Kim) throws a fit when she learns that she’s been dubbed as a “sexpert” — a title she’s not entirely thrilled with. But her new publicist (Tia Mowry-Hardric) reveals that if Karen wants to land another book deal, a flavored-condom journey will lead her there. But Karen’s not the only one with a career-driven dream. April (Rochelle Aytes) also has big plans, and they involve getting into the elite art fellowship she’s dreamed of since her teenage years. And luckily for April, she has a connection that could help her get one step closer to her paint-filled goal.

The board member, who also happens to be one of April’s loyal customers, reveals to the aspiring artist that this year’s deadline for the fellowship is in two days, which means April has 48 hours to paint a new piece of art that unveils “who April Mallory really is.” And from the look on April’s face, it looks like she might struggle with uncovering what that means.

Meanwhile, Karen’s feelings about being a sexpert grown even stronger when her title gets her expelled from her “Mommy and Me” class. “Your energy has become a distraction,” the jealous teacher says after her pupils look to Karen for insight instead of her. Karen then complains to her manny Robert (Jerry O’Connell) about how the book is “ruining her life.” But he advises his employer that she should embrace her new title — after all, who says  she can’t be both a medical professional and an expert on sex?

As Karen tries to balance her career roles, Joss decides to spend her day trying on dresses for her engagement party. But it’s Kate who really goes shopping. Harry’s sister reveals that the real reason for her impromptu trip to the States was inspired by her marriage. Before Kate gets hitched to her boyfriend of 10 years, she wants to have a fling to know what it feels like to be with another man. Joss isn’t so keen on the idea, but tells Kate she’ll help her find a handsome suitor — “only if we do it my way,” she bargains.

Still shocked by Kate’s admission, Joss tried to talk about Kate’s “stranger danger” with Harry. “I’m going to stop this!” he threatens, but Joss warns him not to get involved, since she promised Kate she wouldn’t divulge her scandalous plan to anyone. Harry tells Joss that if she doesn’t put a kibosh on Kate’s one-night stand, he’ll interfere — and it’s going to be ugly.

And it does get ugly when Harry tracks down his fiancé and sister (who neglect to answer their phones) with his Find My Friends app. Harry can’t hold his tongue, and as he tries to drag his sister out of the bar, a patron nearby gets involved. A fight nearly breaks out but Joss puts her boxing skills to work and knocks the stranger out, resulting in her and Harry getting kicked out of the bar.

But before the two leave, Kate shares her thoughts on their relationship. Kate tells the judgmental two that they have no right to criticize her especially since Harry is about to marry his ex-sister-in-law. “And last time I checked there’s nothing normal about that,” she says, adding fuel to the fire, since the reason Harry didn’t tell his family was that he knows it’s not normal either.

Joss is hurt by Harry but reveals she too hasn’t told Savi — Harry’s ex. “Is this weird what we’re doing? Yeah, I still haven’t told Savi, but it’s scary. She was only here for a little bit of the trial, but we're not exactly in the best place.”

After her melodramatic night, Joss turns to her friends for advice. “You guys don’t think it’s weird, right?” she inquiries about her relationship with Harry.

“Well, we don’t think it’s weird anymore … You can understand where Kate’s coming from?” April says. “For so long it was Harry and Savi (Alyssa Milano), Savi and Harry. Now it’s Harry and Joss, Joss and Harry. It’s just an adjustment for people.”

“What are we doing celebrating my impending, awkward marriage?” Joss is left questioning, wanting to cancel the party. But her friends advise her against pulling the plug on the bash – and thankfully they did because it’s at the world’s most awkward dinner party that Joss and Harry rekindle their romance. During the middle of their silent dinner, Joss makes a toast, stating that she doesn’t care what others think about her relationship with Harry. She’s in love with him and that’s all that matters. The speech then inspires Kate to tell them what really inspired her final rendezvous.

Kate explains that her fiancé had an affair, which is what sparked the idea that if she had one too, they would be even. Then they both could move forward and get married. But after Joss’ heartfelt and romantic toast, she realized she wants what Joss and Harry have. “[That is] why I called off the wedding,” she dished, revealing that she’s staying in Los Angeles to find the “true love” of her life — a decision that Joss and Harry don’t seem pleased with.

Kate’s relationship isn’t the only one that crumbles in episode 2. April and Marc’s (Rob Mayes) romance deteriorates when she blames the rock and roll star for being the reason why she didn’t get into the fellowship. According to April, Marc ditched his responsibilities in the store for a band tryout (which he got), forcing April to put down her paintbrush.

“Maybe if my thing had matter as much as your thing it would have turned out differently,” she tells him.

But the episode concludes on a steamy note when Karen thanks her manny for helping her embrace her inner sexpert/medical maven with some lip-locking action. Now who didn’t see that coming from a mile away?

“Mistresses” Season 4 Spoilers Joss (Jes Macallan, left), pictured with Kate (Tabrett Bethell), reveals whether she told her sister about her marriage to her soon-to-be husband during Season 4, episode 2 of “Mistresses.” Photo: ABC

“Mistresses” airs Mondays at 10 p.m. EDT on ABC.