SPOILER ALERT: Do not read ahead, if you have not watched “Grey’s Anatomy” Season 12, Episode 4, which aired on Oct. 15.

Maggie’s (Kelly McCreary) hot hookup with intern Andrew (Giacomo Gianniotti) kept the much-promised lighter mood afloat on Thursday night’s episode of “Grey’s Anatomy,” but Stephanie’s (Jerrika Hinton) revealing backstory brought a heartbreaking touch to the doctor’s storyline this season.

When the episode kicked off, Maggie, Amelia (Caterina Scorsone) and Meredith (Ellen Pompeo) scrambled to get their dinner party together, which all three roomies had forgotten about — though that was hardly the biggest crisis among the MDs, as the night approached, starting with Maggie’s morning, which was awakened with the realization that she drunkenly slept with Andrew — a lot. Giving a nod to the long-running medical drama’s pilot, in which the then-intern Meredith slept with doctor Derek (Patrick Dempsey), Maggie and Andrew’s one night stand continued into more rendezvousing throughout the episode, which was sprinkled with lots of sex talk among the ladies.

April (Sarah Drew) wasn’t so hot and heavy on the dinner party, as she was worried that her estranged hubby Jackson (Jesse Williams) would be in attendance, along with Arizona (Jessica Capshaw) who was equally freaked out that her ex Callie (Sara Ramirez) may bring her new mystery girlfriend — who, at episode’s end, was revealed to be Penny (Samantha Sloyan), a somewhat familiar face for true “Grey’s” fans, who may have recognized her as the doctor working at the hospital where Derek died in Season 11.

Back at Grey-Sloan Memorial Hospital, Stephanie was working under Amelia on a case that proved to touch too close to home for Dr. Edwards. While rehabilitating a patient who’s had brain trauma and has trouble moving her body, Stephanie broke down, disclosing her painful childhood: as a young girl, she was put through a sickle cell clinical trial for years, which forever tainted her. When she had to force the brain-damaged patient to move through unbearable pain, her own memories rushed back. To make matters worse, a very jealous Jo (Camilla Luddington) told Amelia that Stephanie is lying, causing a rift in their friendship, which Hinton says won’t be easy to quickly repair.

Here, Hinton tells Variety an incredible behind-the-scenes story about her character Stephanie’s backstory. Plus, the actress teases what’s to come with her relationships with both Amelia and Jo, now that her history has been revealed.

Shonda Rhimes has said for a while that Season 12 would finally be when viewers learn more about Stephanie. What was your reaction to her backstory?
When we got the script, one of the things that I found interesting, in terms of why this is so triggering for her, is there something about the physical pain that is a very specific trigger for Stephanie. One of the early steps in making sense of the story for me was figuring out, what is it about this patient? Why is this different? I really do think it’s something about the physical pain of this woman. She’s being forced to push this women through such physical pain, and that’s the trigger for her and her childhood — that connects to what she went through as a child with the sickle cell trial and the traumatic things they’d do to her [like] being strapped to a table, being pricked with needles. It was a trial that lasted for a few years.

You actually pitched Stephanie’s backstory because your own cousin went through a traumatic sickle cell trial when she was a child, which really affected you. And now, she’s a doctor! How was the pitch process for such a personal event?
I pitched this story last year. I pitched it Shonda [Rhimes]. It’s scary as hell. It’s terrifying. When you pitch something so close to home and then they actually let you do it, everything perks up in your head that makes you feel insecure. She had let me know immediately that she liked the idea, she was fond of it. At that moment, that was all I really wanted to know. I was just eager to have a backstory for Stephanie, and I really wanted one that I could connect to. It wasn’t until a meeting a few weeks before we got the script that they said we’re cultivating that idea.

Since you experienced your family going through that trauma, you must have had a deeper understanding for Stephanie’s pain in this episode?
It’s so obvious to say that itdoes something to you. Even though you may not process it as a child, that kind of respoinsibility and what’s being done to you, even though it may feel terrible, what’s being done to you is going to be used to help millions of other people — hopefully, if it goes right.

Why was it so difficult for Stephanie to treat the brain trauma patient?
When she was a child, she felt like she was being punished for something that she couldn’t control, and she doesn’t want to do to a patient.

Now that her backstory is revealed, how will Stephanie be different, going forward?
I think you’ll learn, it’s kind of an integration in the way that you’ll continue to learn about her. The more information you get about a person, the more that informs you about why they make the decisions they make in the moment. Going forward, it’s not so much about overt backstory, but now you have context to watch and see why she does what she does, and why she may have a particular thing about wanting to feel empowered and wanting to be in power. She says something very specific that she doesn’t talk about it because she’s not a patient anymore — she’s a surgeon. She’s in a position of power. I think that’s really important for her. A lot of kids who spend a lot of time in the hospital as a child, they go into the medical industry.

Jo betrayed Stephanie by saying that she was lying about her childhood. Where does their relationship stand now?
Icy as Antartica! It’s cold. That sh-t is really cold. Stephanie is completely betrayed. She revealed such a vulnerable piece of herself. They’ve known each other for a few years now and I think it’s been a very one-sided friendship — Jo has offered up a lot of herself to Stephanie, but Stephanie has never shared as much as Jo as. Stephanie says I only tell people I trust. That’s a huge bombshell for me, as a character so for her to drop this huge bombshell with Amelia who she’s very close to and for her to tell Jo and for Jo to immediately not believe her, that’s an outstanding betrayal. That’s where the baseline of their coldness starts. In order for them to really earn their friendship, it’s going to be icy for a while. We’re going to see that play out. We’re going to see what happens when the two surviving residents from our class kind of loose each other.