Once a cheater, always a cheater, right? Episode 16 of “Grey’s Anatomy” will explore that concept when the hit ABC series airs its upcoming installment named after the Crowded House single, “Don’t Dream It’s Over.”

When episode 15 concluded, fans of the Shonda Rhimes medical drama were left with a major cliffhanger: Did Derek (Patrick Dempsey) sleep with another woman? After Meredith (Ellen Pompeo) came to the conclusion that she’d rather share her success with her husband than bask in it alone, she called her beloved hubby to express her feelings, but when she dialed his number a mysterious woman answered. “Who is this?” Meredith questioned over and over again until the unknown person on the end of the line hung up.

Meredith will be forced to face her “biggest fears about Derek” in episode 16. According to the promo video for “Don’t Dream It’s Over,” Mer is frightened that Derek might break his vows such as he did with his former spouse Addison (Kate Walsh). “He’s done this before,” Meredith tells Alex (Justin Chambers). “Met a girl, fell in love, started over,” she says, referring to how Derek left his wife to be with her. In a moment of weakness, Meredith asks her “person” if her husband could have possibly met someone else while he’s been working in Washington, D.C. “He’s not cheating on me, right?” she asks, not ready to hear the answer.

But fans can expect more than just MerDer drama to occur in the upcoming episode. According to the synopsis, “a patient’s condition sparks conversation between Richard (James Pickens, Jr.) and Maggie (Kelly McCreary).” Viewers will also watch April (Sarah Drew) and Jackson (Jesse Williams) “struggle to return to their normal lives” since the death of their child. In episode 11, the couple said goodbye to their son (who they named Samuel) after the child was born with Type 2 of osteogenesis imperfecta, a brittle bones disease that took their baby’s life in 43 minutes. “He squeezed my finger and then he let go,” April said of the moment her son’s short life ended. Since their baby’s death, April and Jackson have eased their way back into work, but, of course, the tragic event still weighs heavily on their hearts.

The summary for episode 16 added that Arizona (Jessica Capshaw) will face the reality that Callie (Sara Ramirez) has moved on. And to think that Callie was the one initially jealous of Arizona’s sexless rebound buddy Dr. Herman (Geena Davis). According to a sneak-peek video, Callie’s ex will catch her locking lips with another woman in the upcoming installment after their date gets cut short. “I’m just trying to prolong our half-date,” Callie’s date jokes, adding that she should have seen it coming because the trauma doctor’s profile did say “crazy hours.” “And you’re off to go save a life? What’s hotter than that?” The blonde then lays a kiss on Callie, one that Arizona witnesses through the window of a door.

“Grey’s Anatomy” Season 11, episode 16 will air on Thursday, March 19, at 8 p.m. EDT on ABC.