While Merritt ends up not being able to escape after almost doing so in the previous episode, she does finally get some answers as to why she's been held captive for the past four years. And it all has to do with people from her past. We've got a recap of what happens in Dept. Q episode 8, which is the penultimate episode, on Netflix. Spoilers below.
It's all about Harry Jennings in Dept. Q episode 8
Merritt doesn't manage to escape as she'd hoped, though we learn more about the man who has been with the woman in her kidnapping this whole time. He fixes the door and weirdly tells her he loves her. Ok. He takes Merritt's necklace which we learn is very important to her as it's from her mother.
In the flashback, we also see Merritt and Harry together. As a reminder, he's the one who beat up William on that fateful day. They were in a relationship and talk about running away together. He also reveals his mom is a bit crazy, being the one to almost burn their house down. Though that gets blamed on Lyle, even though he and Harry weren't even home that day.
To get by, they'd need to steal one of her mother's rings to sell and have enough money to live off of. Though Harry thinks about doing it, saying people believe he steals from them anyway, Merritt tells him not to. Though it seems like he doesn't listen to her and goes in to rob them anyway, with William being unluckily home.

Flash forward to the present and Merritt's captors are Harry's mother Ailsa and his brother Lyle Jennings. Plus, Lyle took the identity of Sam Haig and that's who Merritt thought she was seeing. They blame her for Harry's death though she's unapologetic because of what Harry did to her brother. She also finds out that Sam Haig is really Lyle Jennings. She'd actually told Sam/Lyle to come with her and William on the boat the day she disappears and he knows what time they were to depart, which reveals how he and his mother were able to be in the right place at the right time.
Carl and co. are close to figuring this out too as they realize that the Sam Haig who was with Merritt and the Sam Haig with Chloe, the rock climber's wife, are two different people. Which again, leads us to believe Lyle had taken the real Sam's identity. Did he end up killing Sam?
Merritt says that Harry told her his brother wasn't right in the head. And clearly he isn't for impersonating another person and coming up with this plan with his mother. The real Sam Haig is also the person who beat up Lyle Jennings in the facility, which the Dept. Q crew now know.
Be sure to check out all of our episodic recaps of the series, here. Dept. Q is now streaming on Netflix.