From TVLine: https://tvline.com/2021/10/15/you-recap-season-3-episode-1-natalie-dies-death-explained/

You S3 Ep 1:
And They Lived Happily Ever After

By Andy Swift / October 15 2021, 12:00 PM PDT


From the moment Joe Goldberg first spotted his new neighbor in the closing moments of YOU‘s second season, it was clear that he had found his new obsession.

Lo and behold, the Netflix thriller’s third season — which is now available to stream in its entirety — finds Joe getting extremely close to that mysterious woman on the other side of the fence. Natalie (played by Michaela McManus) turns out to be the deeply dissatisfied wife of a tech mogul named Matthew (Scott Speedman), who’s far too busy with work to notice that his wife is being seduced by the serial killer next door.

And you know it’s love, because Joe even gives Natalie the Beck Special (aka pleasuring himself in public while thinking about her). He also puts on his finest stalker cap and follows Natalie to the library, where she keeps the flirtation going by leaving a book for him at the front desk. So it’s no surprise when Natalie invites Joe over to her home, “accidentally” cuts her hand on a wine glass, then takes him to her reading room for a little bump and grind.

In fact, the only surprise here is that Joe finds the wherewithal to reject her advances, returning home to release all of his pent-up sexual energy on Love. You know, his actual wife. The two women even become friends, with Natalie putting on her realtor hat to help Love find a spot to open her new bakery. Unfortunately — spoiler alert, again! — that bakery is the last place Natalie ever goes. As soon as Love puts the pieces together and figures out that something is happening between Natalie and Joe, she bashes the poor woman over the head… and kills her.

“You do have to keep switching things up,” showrunner Sera Gamble tells TVLine of the big twist. “I’m going to say this, and Future Me is going to be really pissed that I said this out loud: With a show like this, where Season 1 was such a particular fun, twisty ride coming off of Caroline [Kepnes’] book, we really had to prove to you at the beginning of Season 2 that we would still be able to surprise you. So we did a lot of stuff in Season 2 to try to do that. The conversation at the beginning of Season 3 was ‘What do you think would happen if you were a viewer?’ And it’s that Michaela would be in the whole season, so we were like, ‘She’s got to go in Episode 1.'”

For the record, the actors who play Natalie’s killer and the object of her affection are both down with the brutal twist.

“I was into it, because it was like, ‘Oh, this is going to go in some other direction,'” Penn Badgley tells TVLine. “That’s always exciting.”

Adds Victoria Pedretti, “It’s fun when you can subvert people’s expectations on television these days. We’ve all consumed so much of it, so I find that it’s harder to be surprised.”