As a Fridge subpage, all spoilers are unmarked as per policy. You Have Been Warned.
- The music in the trailer is a creepily slow, piano-only version of "Our House (Is a Very Very Very Fine House)".
- Crossing over with Twin Telepathy: In episode 4, the reason Luke keeps rubbing at the left side of his neck after that night, why he's feeling like he can't get warm and like his joints and limbs are all stiff is because Nell is dead of a broken neck and her spirit has been trapped by Hill House.
- Luke is desperate to help Joey to the point hell steal from family and ignore the signs that she is not really committed to being helped. He probably unconsciously sees Abigail in her - another friend of his no one believed in (more literally in her case) who he had to watch die of poisoning.
- The House needs weakness or sensitivity to prey on to manipulate its victims. The children are all young and impressionable, so all of them are in its sway. Olivia is sensitive to the paranormal. As an adult, Luke is only snagged by the House after seeing Nell for the first time, distracting him. Of all the Crains, only Hugh, who is an adult with a strong, practical mind, is relatively unscathed. His lone concession to the House is a willing, rational and calculated bargain to protect his kids.
- In episode 3, Theo has a vision/nightmare of Mr. Smiley pulling off her blankets while she sleeps, which is terrifying enough on its own, but then we learn that Mr. Smiley is actually her patient's way of compartmentalizing her foster father's sexual abuse. Who came to her bedroom at night. And would probably begin his abuse by removing her blankets.
- One of the photos of Kelsey and her foster father shows him smiling and her with a blank expression. He's later revealed to be Mr. Smiley, her tormentor. Also, if you pause the screen on Kelsey's drawing of her family, you can see that Rich's right eye is twice the size of his left. Just like Mr. Smiley.
- Luke's speech in Liv's vision about "putting poison in himself" initially just seems like an appropriately childlike metaphor for his future heroin addiction. Then, in the final episode, the House compels him to literally inject rat poison into his veins.
- Steve is criticized by several family members for getting details wrong in his original The Haunting of Hill House book. In the end, we learn that the kids were experiencing the House differently, so their stories would never match up no matter how accurately Steve wrote them.
- In episode 9, Poppy says that she loves what Olivia did with the room, and then mentions that "it was a dressing room for me, then a nursery." At first it can be easily written off as Poppy describing how she set up the room herself, until you realize the wording... she's telling Olivia what the Red Room turned itself into for her.
- In episode 5, Shirley mutters in her sleep: "dancing in the red room." This is not a future prediction as it first appears: it is a very, very early hint as to the nature of the Red Room, because for Theo, it was a dance studio.
- In the show's first episode, we hear narration from Steve's Hill House book, describing the environment as dark and for the lack of a better word, haunting, and with themes of logic, ending with the line "And those who walk there, walk alone". However, in the show's last episode, the season closes with a similar narration but instead discusses the power of love and ending with the line "And those who walk there, walk together". The season begins and ends with Steve's Hill House book to show how in the beginning, he was alone as he had isolated those he loved and was in denial that any hauntings happened on the final night at Hill House, however by the end of the season, not only does Steve understand the truth of what happened on the final night at Hill House, he is finally not alone and is with his family, something it took long enough for him to realize.
- In Episode 10, as Hugh embraces Nell and Liv in the Red Room, Nell is the only one hugging him with closed eyes. Olivia on the other hand keeps her eyes locked on Steve as the Red Room's door closes, implying she still wants her kids to die and be with her, despite the fact they'll all be trapped in Hill House forever.
- A more sympathetic interpretation of her stare could be that Olivia is watching Steve walk away, knowing that she'll never see him, or any of her living children, again.