'Mistresses' season 4 spoilers, plot news: Lines become blurrier in the upcoming episode as someone from Marc's past returns

Karen (Yunjin Kim) decided she can't stay away from her nanny, and someone from Marc's (Rob Mayes) past has come back to beg for a second chance.

The last episode of "Mistresses" showed what happens when someone drinks a few glasses of wine. Apparently, judgment gets fuzzy and lines start to get blurred. That's exactly what happened to Karen and Robert when the employer-employee line was breached.

Employed as Karen's babysitter, he seemingly overstepped his boundaries when he started telling her what she ought to do in the "babying department." Hence, he was fired from the job.

Still, Karen realized she was better off with Robert as her lover than her babysitter, so they made amends and rekindled their romance.

Nevertheless, if the synopsis shared by Carter Matt is any indication, it looks like Karen was able to knock some sense into herself and decided to put her love life on hold.

"Karen realizes she's very happy to be back working with her clients again, despite putting her love life on hold. April's new client gets a little too close for comfort, while someone from Marc's past becomes very present. Kate struggles after learning her ex-fiancé is dating someone else, while Joss plays dirty to get a new client," the synopsis read.

It seems April's (Rochelle Aytes) client, Michael (Ian Harvie) would make their business arrangement a tad too personal. The promotional clip for the next episode, aptly titled "Blurred Lines," also show Marc's rocker ex-girlfriend coming back to beg for a second chance, in Marc and April's doorway, no less.

Will Marc succumb to her plea? How will April react? Moreover, there's a possibility that Joss' (Jes Macallan) pent-up anger would finally explode at the worst possible time â€“ while she's "aggressively pursuing" a new client.

"Mistresses" season 4 airs Mondays, 10 p.m. EDT, on ABC. Check out the clip for the upcoming episode below.