The season 3 finale of The Affair is a trip to Paris. I assume literally, as we jump forward in time indiscriminately and it doesn't seem that Noah (Dominic West) at any point saw a therapist or psychologist about his break with reality, so we'll just take it on faith that this isn't a Vanilla Sky-scented dream.
Now we're in Noah and Juliette's (Iréne Jacobs) affair — with the reminder that she does have a husband back in Paris, where Noah joins her. What he doesn't expressly say, but the subtext of the season tells us is that the latest woman he's looking to to fix his life is Juliette. All those explainers we got about how Helen (Maura Tierney) and Alison (Ruth Wilson) were his escape are the map that gives us all the insight we need into this affair.
Juliette is in crisis (as was Alison when that affair began) because she's returned home where he husband, who is much older and suffers from Alzheimer's, passes away. Just before, the integrity of his academic work comes into question. This is where it is revealed to us that Juliette worked with him. Thus the stain of that doubt falls on her work as well. I'd love to see more about Juliette's academic work next season, along with her French views on sexuality. The end of her scene makes it seem like her relationship with Noah could easily carry on into season 4.
As for Noah, once we're past his slightly different but mostly the same retellings of his time with Juliette we see him meet up with his daughter, Whitney (Julia Goldani Telles). She's in town helping her very lame, much older artist boyfriend Furkat (Jonathan Cake) open a show. Noah tries with all his might to connect with her, but he sucks at it. Until that is, he witnesses them have a fight and sees Furkat slap her across the face. He follows her demands not to retaliate and leaves the scene with her, but immediately says, "That's not okay, right?" He knows he's been a terrible male example for her, and legitimately isn't sure if she knows that a man slapping her face is not okay. At any rate, it leads to a new beginning in their relationship. A question, however: We are never told if Helen let Whitney in on the news that she killed Scotty Lockhart so...did she? One assumes yes since Whitney was able to make any steps towards forgiving Noah, but it's an odd thing to have happen off screen.
In the end, Noah takes Whitney home and drops her off at her mother's house, which is all decorated for the holidays. Helen and Noah exchange a very parental look and part.
See you in season 4, try to stay connected to reality until then.