Not five minutes into the TV series Game of Thrones, we were treated to the charming image of an adorable, cherub-faced young girl with big blue eyes…impaled to a tree…who turned out to be a zombie. Since then, we’ve witnessed a number of truly shocking scenes on HBO’s ultraviolent show. Talisa Stark, eight months pregnant, being knifed in the belly during the Red Wedding; Khal Drogo ripping the tongue out of Mago’s head; Joffrey forcing his betrothed, Sansa, to gaze at the decapitated head of her father, Ned Stark, mounted on a spike; the castration of Theon Greyjoy; and even the death of a newborn baby—in a whorehouse.

But, as far as sheer quantity of taboo-breaking goes, Sunday night’s episode may have boasted the most disturbing sequence in Game of Thrones history. In fact, when you put it in context, it may be the most screwed up sex scene ever broadcast on television.

On the third episode of Season 4, “Breaker of Chains,” Jaime Lannister (Nikolaj Coster-Waldau) rapes his sister, Cersei (Lena Headey), over the altar of their dead son, Joffrey Baratheon.

“It is fucked up,” Coster-Waldau tells The Daily Beast. “It doesn’t get any darker than that, does it?”

The tension had been building between the two incestuous lovers for quite some time. Jaime “Kingslayer” Lannister had, after a long incarceration, returned to King’s Landing with one hand. He’s no longer the rakish, swashbuckling stud of yore, and his sister-lover, Cersei, is far from impressed by the new Jaime. “You took too long,” she says, rebuffing him. Then came the mysterious poisoning death of their secret son, Joffrey, which forces the two parents together once more, albeit while grieving.

So they find themselves situated in the Great Sept of King’s Landing, gazing upon the “Mother’s Altar” of Joffrey. They listen to their shrewd father, Tywin Lannister, smear their dead son in front of his corpse.

“Your brother was not a wise king…Your brother was not a good king,” Tywin tells young Tommen Baratheon, the next in line to the throne. “If he had been, perhaps he’d still be alive.”The two walk off, and Jaime asks for a moment alone in the place of worship with Cersei, as they stare in disbelief at the body of their dead son.

“Avenge him… avenge our son,” shrieks Cersei. “Kill Tyrion.”

“Tyrion’s my brother…our brother,” Jaime replies. “There will be a trial to get to the truth of what happened.”

“Please, Jaime, you have to…he’s our son…our baby boy.”

Jaime embraces Cersei and the two begin to kiss. Then, Cersei catches sight of his golden hand, and recoils.

“There’s a moment in the scene where the hand comes up and she has this face of disgust, and Jaime says, Why have the Gods made me love a hateful woman?” says Coster-Waldau. “He wants her, and wants everything to go back to the way it was. But there’s no way back.”

And then Jaime attacks Cersei, ripping her dress. She yells, “Jaime, not here…please…stop it!” Her objections fall on deaf ears, and he throws her first against the altar of their dead son, and then to the ground beside it.

“To understand the psychology behind it, and why he goes as far as he does, was really difficult,” says Coster-Waldau. “To me it became, When does physical desire take over? It’s one of those things where he’s been holding it back for so long, and then out of anger he grabs her, and instinct takes over, and he lets loose. He says, I don’t care. He wants to not care. He has to connect to her, and he knows this is the most fucked up way for it to happen, but in that moment, he knows it’s all he can do. It’s an act of powerlessness.”

Indeed, after Cersei yells, “Stop…it’s not right!” Jaime mutters back, “I don’t care,” as he thrusts away at his sister next to the body of their dead son. The last image we see is her hand grabbing Joffrey’s altar sash, as she yells, “Stop!”“It was tough to shoot, as well,” says Coster-Waldau. “There is significance in that scene, and it comes straight from the books—it’s George R.R. Martin’s mind at play. It took me awhile to wrap my head around it, because I think that, for some people, it’s just going to look like rape. The intention is that it’s not just that; it’s about two people who’ve had this connection for so many years, and much of it is physical, and much of it has had to be kept secret, and this is almost the last thing left now. It’s him trying to force her back and make him whole again because of his stupid hand.”

The scene plays out differently than the source material, A Storm of Swords—author George R.R. Martin’s third novel in his series A Song of Ice and Fire, upon which Game of Thrones is based. In the novel, the sex scene between Jaime and Cersei is more consensual. But here, it seems anything but.So is it rape?“Yes, and no,” says Coster-Waldau. “There are moments where she gives in, and moments where she pushes him away. But it’s not pretty.”

He adds, “It’s going to be interesting what people think about it.”