Quote: Davida Grimes @ 15th March 2017, 12:10 AMOkay, so here's my guess about what happened. (SPOILERS btw)
Reece's character is definitely obsessive, and also traumatized by past events to the point of blocking out the memories of his son's death (I'm thinking he either killed the son, or unintentionally was responsible for him dying), and then blocking out the violent act he committed at the end. The end was ambiguous between him having killed the guy to get the shoe back, and him having killed the daughter so that the twins can be together. The shoe guy was in Norfolk, and Keeley Hawes' character made it sound like that was far from wherever they were, but the blood on his hand was still wet. So he could have killed the shoe guy AND the daughter to reunite the twins, or he could have just killed the daughter, or just killed the shoe guy. I'm not leaning toward one of those three options in particular at this point. I think it's supposed to be ambiguous.
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I took it as them making us assume he'd killed the shoe guy, but in fact killed the daughter, backed up when he says that he "wanted them to be together again". It's so easy to overthink No. 9 to the point of seeing things that aren't there. I think it was an outstanding evaluation of a state of grief, and on a rewatch there's so many hints, the amount of symmetrical twins (chairs, lamps etc).