Joss (Jes Macallan) and Harry's (Brett Tucker) amazing start in Las Vegas may not last long in the sixth episode of "Mistresses" season 4.

In the sneak peek for the episode titled "What Happens in Vegas," the engaged couple learned that the hotel room they got was paid for by Harry's new business partner Jonathan Amadi (Navid Negahban) in Las Vegas.

Joss was excited when she found out that they will stay in a room with the best view in the city, and they also saw several gifts from Jonathan lying on the table. They even saw a stack of chips that they can use for playing. While Joss believes that everything is too good to be true, Harry just reassured her that Jonathan was just an overly generous host and advised her to enjoy being pampered during their stay in Sin City.

But the clip also showed that Joss was right about her suspicions about Jonathan, since she saw him hurting a woman down the hall. She tried to intervene, but the wealthy Persian businessman told her to mind her own business. Will this affect Harry's business partnership with him?

Meanwhile, Karen's (Yunjin Kim) mysterious and unexpected guest will be finally revealed in the upcoming episode. It appears that Alec (Ed Quinn) decided to drop by and reveal an explosive news that will have a huge effect on Karen's life.

The synopsis for the episode reads: "Alec makes a surprise visit and turns Karen's life upside down when he reveals something new in his life. April and Marc butt heads when it comes to parenting Lucy, putting a strain on their relationship. Kate discovers her new love interest has close ties to Joss and Harry. Joss and Harry get invited to Las Vegas by Harry's new business partner, Jonathan, and Joss snaps unexpectedly just before they are to be married."

The sixth episode of "Mistresses" season 4 airs July 11 on ABC.