The Woman in the Wall 
Lorna Brady wakes one morning to find a corpse in her house with no idea who the dead woman is. She doubts herself, because she has long suffered from extreme bouts of sleepwalking.
The Woman in the Wall: S1 E4: ""The Cruelty Man" Season 1, Episode 4
Lorna's and Colman's separate agendas begin to dovetail, bringing new insights for each of them.
The Woman in the Wall: S1 E3: "Knock Knock” Season 1, Episode 3
A survivor's funeral puts Lorna on edge. Hope then comes through unexpected information about Clemence's daughter.
The Woman in the Wall: S1 e2: Show Thyself Season 1, Episode 2
From IMDB: "When Lorna has no intention of sleeping until she finds out what [name redacted] knew. The town's laundry survivors are campaigning for justice. Past betrayals emerge to the surface and end in tragedy." [more inside]
The Woman in the Wall: S1 E1: Back to Life Season 1, Episode 1
Summary from IMDB: "When Lorna Brady wakes to find a corpse in her house, she has no idea who the dead woman is or if she's responsible for the apparent murder; retracing her steps, Lorna realizes that the mysterious woman could be linked to her past."
There are two mysteries here. One is a police procedural concerning a current crime or crimes. The other concerns Lorna-- a survivor of the Magdalene Laundry system whose child was stolen from her and who is dealing with heavy emotional fallout, to the point where she cannot trust her own perceptions, giving her half of the story an eerie quaility.
Review from the New York Times (gift link) may be spoilerific