Joss (Jes Macallan) is still elated over Harry's (Brett Tucker) beachfront proposal during the premiere episode of "Mistresses" season 4, but this may go downhill starting episode 2.

In the episode titled "Mistaken Identity," Harry's sister Kate (Tabrett Bethell) will travel to California all the way from Australia for her brother's engagement. But instead of joining the celebration, Kate's arrival will cause trouble for the newly engaged couple.

Based on the trailer for the upcoming episode, Kate will point out why she just cannot be happy for Harry and Joss' relationship during Joss and Harry's engagement dinner.

"Marrying your ex-sister-in-law? There's nothing normal about that," Kate told the couple in front of all their guests. "You really think everyone is going to celebrate this?"

Harry used to be married to Joss's sister Savi (Alyssa Milano), but their disagreements about building a family eventually led their 15-year marriage to a divorce. Kate finds it weird that the former siblings-in-law will decide to begin a new life together.

Kate's opinion seemed to have an effect on Joss, since the real estate agent was seen asking for her friends' views regarding her decision to marry Savi's ex. But based on Karen (Yunjin Kim) and April's (Rochelle Aytes) reaction in the sneak peek, they also agreed that the upcoming union would be a little awkward.

The official synopsis for the upcoming episode reads:

"Harry's sister Kate surprise visits Harry and Joss and exposes problems she is having with her fiancé. Meanwhile, Joss struggles with celebrating her engagement with Harry. April gets an exciting opportunity to apply for a painting fellowship, while Marc has success joining a band. Karen struggles with her new role being known as a 'sexpert,' and she gets closer with the male 'manny' Robert."

"Mistresses" season 4, episode 2 airs on Monday, June 6, on ABC.