Thanks to a relatively revelatory penultimate episode, Harlan Coben's *Run Away* doesn't have a great deal to do in its finale. Episode 8, "It Stays With Us," only has one big question to answer: who killed Aaron Corval. But of course, it isn't content to do just that, and includes a series of late reveals that leave the season's ending with a note of ambiguity. However, everything else is resolved pretty neatly, which is more than you can say for most Netflix shows.

I hope you've been reading all of these recaps, since a lot of what's going on here loops back to things that might not have been mentioned for several episodes. It's a lot to unpack, but I'll do my best to keep it all simple and coherent. So, without further ado, here we go.
Simon, despite having been shot, manages to get a message through the responding officers to Isaac. Rocco's tip-off that Paige got a bus to Backmere, which is close to the Shining Haven, aka the headquarters of the Beacon of the Shining Truth, suggests that she might be there. And as luck would have it, the police are in the process of raiding the place.
After clearing out the security and rounding up the civilians, Isaac finds a secret room that leads him directly to Caspar Vartage, who is intending to take his own life rather than go through the courts. He's dying anyway, and is satisfied with having lived three decades of his life as a king, as well he might be. But Isaac isn't letting him get away that easily and disarms him of the deadly pill.
Outside, one of the women mentions that a new girl arrived recently and has been kept in a shipping container the cult uses for "solitary confinement." What a dismal place! There is indeed a girl in there, but it isn't Paige. Instead, it's a girl named Eve, whose real name is Zara.
Isaac makes a bold move, visiting Simon at his hospital bedside to breach police protocol and spill the beans on the entire investigation. He shares with Simon the tale of Caspar and his half-brothers, all found through ancestry websites. Isaac speculates that Ash and Dee Dee are responsible for Aaron's death, which we all know they're not, and that the mysterious woman from the balcony has vanished without a trace, at least as far as Isaac is concerned.
Simon, however, has seen her. Adiona paid him a visit in the hospital before Isaac arrived and shared her story with him, about how she sired two sons with Caspar, the second of which was sent away. She used an ancestry website to track him down. This was Nathan Braddrick, the man we saw her approach in the previous episode. She couldn't let her own son be murdered, which is why she tried to intervene in Ash and Dee Dee's mission.
However, this isn't exactly redemption. If her own son hadn't been in danger, she wouldn't have cared much about anyone else. When Simon visits Ingrid in the hospital, he finds Paige at her bedside. She's been in rehab for a month and is nearly a month clean. She only left after hearing about what happened to her mother and plans to get back as soon as possible before she succumbs to temptation.
Paige explains to Simon that after finding Aaron's body, she ran, hid, and then checked into a rehab that Ingrid had introduced her to (another family secret). Paige swore her to secrecy since she didn't want to let Simon down if she failed again. During her first stay at the facility, Aaron had found out where it was and injected her with smack while she was asleep. What a charmer.
Simon agrees to take Paige back to the rehab. Before she re-enters, though, she confesses to killing Aaron. Simon doesn't believe her and asks if she went to Ingrid after Aaron beat her. It turns out she did. When she returned to the flat, Aaron was already dead.
Eventually, Ingrid awakes from her slumber. Simon, Cornelius, Isaac, Ruby, Maria, Lou, and Daisy all gather for Elena's funeral after her body is discovered by the serene lake. Paige emerges from rehab and reunites with her family. All seems well on the surface, but beneath the calm lies a storm.
Simon, however, cannot rest. Despite his promise to Paige that he would let the past be, he confronts Ingrid about Aaron's murder. She confesses, revealing that she used Jay as an alibi - just an alibi, she emphasizes - and slipped away from him through the back door of Busy Burritos. She killed Aaron in the style of a gang killing she had read about and then fled. Luther witnessed her departure, which explains his terror when he saw her again at the end of Episode 1.
This doesn't fully explain why Jay told the police that she had gone to his apartment after giving him the slip in Busy Burritos. I suppose that's just an oversight. But there's more to this story than meets the eye.
The ending of Harlan Coben's Run Away saves one final revelation for the very end. And this, once again, involves Ingrid.
Simon enquires about Ingrid's modeling days from Yvonne. She directs him in the right direction, but what he sees visibly shocks him. He goes home and shares this revelation with Paige, who is playing the guitar in the garden. He mentions that there were two single mattresses in Aaron's flat (how's that for a kick-yourself clue?). What kind of teenage couple sleeps in separate beds?
A teenage couple who are brother and sister! Simon also reveals that he spoke to Doug, who said that while he was being attacked, his attacker was screaming, "Nobody hurts my sister." Paige and Aaron weren't a couple; they were half-siblings. Ingrid's "old modeling photos" reveal her as a member of the Shining Truth. The One sired Aaron with her.
After leaving the cult, Ingrid went to rehab - the same facility she ultimately took Paige to. But what this means is that Ingrid isn't just guilty of murder; she's guilty of murdering her own son. Paige begs Simon to keep this secret. Living up to the title of the finale, "It Stays With Us," Simon and Paige agree to keep their secret.