Things are going to get dark in Thursday's episode of "Grey's Anatomy", as Meredith will struggle to accept Penny, the doctor who was attending to Derek the night he died.

Last week's episode ended with Callie bringing her new girlfriend Penny to a dinner party at Meredith's house, and it looks like coming face-to-face with Penny will be traumatic for the widow.

In a promo for the episode, Meredith is seen running upstairs and fighting an urge to vomit as soon as she meets Penny, and it looks like Alex will pry the truth about Callie's new girlfriend before Meredith loses it completely.

The promo video also shows Meredith recounting the words Penny said the night Derek died, and she apparently comes to the conclusion that it was Penny's incompetency that led to her husband's death.

"It was my job to save him. And I failed," Penny said. "And now he's gonna die. Because I was not a good enough doctor to keep him alive."

Elsewhere in the episode, fans will see April taking over kitchen duties in a bid to avoid meeting her estranged husband Jackson. Fans are divided on whether the two should end their marriage for good, and according to actor Jesse Williams the two should really talk about the issues plaguing them before pulling the plug.

"I think that for the most part, the process is far more important than the end game," the actor told Parade. "Them having this real obstacle in front of them and really talking about it and really hearing each other and really learning about each other and learn about selflessness and what collaboration is and what marriage is. They need to learn how taking care of yourself at the cost of someone else is different than just taking care of yourself. If they were to break up, I wouldn't want that because I really like the work that we do together, Sarah and I. But if they do break up,I want them to have really exhausted it and tried and communicated."

"Grey's Anatomy" airs Thursday nights at 8pm EDT on ABC. The official synopsis for the episode reads:

In the midst of the sisters' dinner party, Maggie ditches her cooking duties to rush to the hospital. Meanwhile, April steps in to help cook as an attempt to avoid Jackson and Arizona nervously waits to find out more about Callie's new girlfriend.