Richard Armitage's character, William, gets into an affair with his son's fiancée -- played by actress Charlie Murphy -- and at one point in the mini series, he ransacks a hotel room that she had just stayed in ... desperately looking for any lingering sign of her left behind.

Eventually, he finds a pillow on the bed where she slept and picks up her scent ... which then launches him into a full-blown sex act where he's going at it with the cushion, literally. The dude sniffs it up, bites it and humps it like a dog -- as if it was the actual person.

That's where Netflix fans seem to have drawn the line on the kinkiness ... several took to Twitter to express their disgust, joking that they'd never look at another hotel pillow the same way again. That's probably a good rule ... but "Obsession" takes it to a new level.

Of course, a lot of folks are joking with their gross-out takes -- posting funny memes/GIFs to react. Some, it seems, even thought it was pretty hot! To each their own, we suppose.

Here's the crazy part ... the dude himself, Armitage, actually says this scene was largely improvised -- which just speaks to how good of an actor he is -- seeing how damn into it he was on camera. He explains that they were going to do a lipstick thing, but thought the pillow would be more realistic and jarring ... considering how much of a sex fiend the character is.