It was only a matter of time before “Grey’s Anatomy” creator, Shonda Rhimes, broke out the heart-wrenching Season 12 drama – and that’s exactly what fans of the hit ABC series can expect during episode 5, titled “Guess Who’s Coming To Dinner?" According to the synopsis for the upcoming installment, audiences can expect the witty storyline to take a dark turn as Meredith (Ellen Pompeo) is forced to come face-to-face with Derek’s (Patrick Dempsey) killer.

OK, maybe calling Penny (Samantha Sloyan) a murderer is a stretch. But she herself stated how she was responsible for McDreamy’s demise due to not being a “good doctor.”

During Season 11 of “Grey’s Anatomy,” Penny was tasked with healing Derek when he was brought to the hospital following his car crash. Ultimately, Penny was unable to save the beloved surgeon, leaving Derek’s children fatherless and turning Meredith into a widow – a title Mer finally came to terms with in episode 4, that is, until Callie’s (Sara Ramirez) new beau walked through the door.

When Mer sees Penny’s face – a face she’ll never forget – she begins to have flashbacks from the night her husband died.

“It was my job to save him. And I failed,” Meredith recants what Penny said to her from the Season 11 episode. “And now he’s gonna die. Because I was not a good enough doctor to keep him alive.”

In a sneak-peek video, fans watch as Meredith reacts to Penny’s surprising debut by flipping over the photos of her late husband and running up stairs to the bathroom after encountering the urge to vomit.

She splashes cold water on her face but the traumatic memories continue to flood her memory. Hopefully Alex (Justin Chambers) can piece together what’s bothering his friend before it’s too late. In the promo video, viewers can see Alex suspiciously watch Mer sprint up the stairs – and seeing as he’s her “person” (a title he gained since Cristina [Sandra Oh] left), we have a feeling he can sense something’s not right.

“Grey’s Anatomy” airs Thursday nights at 8 p.m. EDT on ABC.