Wow, so this was a pretty interesting episode!
Interesting things to note in hindsight of this episode:
- Cecil previously once mentioned missing his mother - implying that she had died, but never actually stating it
- Cecil also mentioned his mother warning him as a small child that one day he would die, and it would have something to do with a mirror
So, what happened in this episode? Or, to list the main question posed following this episode:
- Why does Cecil have no memory of recording the tapes, or any recollection of the events or individuals 'he' recalls in the tapes?
- Why does the 'Cecil' in these tapes mention a 'brother' who doesn't exist?
- Why did Cecil's mother and brother disappear?
- Why, in the weeks prior to her disappearance, did Cecil's mother obsessively cover all the mirrors in the house, preventing Cecil from seeing his own reflection?
- Who or what was pursuing Cecil over the course of these recordings?
- Who or what attacked Cecil during his final recording?
- Why was the radio presenter being 'really nice' to Cecil in the buildup up to this? Did he know something was going to happen?
- Was there any significance in Cecil viewing his own reflection and remarking that he felt he had changed somehow and the consequent attack?
- Why does Cecil not remember any of this?
The obvious object of significance in these questions and the episode itself are mirrors.
Now, mirrors, in both horror and spirituality, are pretty significant. Anyone will be aware of the common pop-culture horror associations with mirrors - legends such as Bloody Mary, for example, or of vampires being unable to see their reflection - but there is also a lot of spiritual associations with mirrors in modern traditions and superstitions. Some spiritualists believe that mirrors can act as a portal or a 'weak spot' to the spirit world. Smashing a mirror is said to bring 7 years bad luck. This superstition itself is linked to the old belief that mirrors can trap souls. And in the 19th century in Europe and America, there was a tradition of covering all the mirrors in the house after a family member has died, in order to prevent their soul from getting trapped in the mirror and being unable to pass in to the afterlife.
Now, looking at these facts, here are my theories:
1. The 'Cecil' we have as our narrator is not the 'Cecil' we have making the tape recordings. The 'Cecil' we have narrating this is in reality the 'thing' that attacked young Cecil during his final recording, who killed young Cecil, and possessed his body. This is why Cecil's family left, and why Cecil retains some memories of his past, but not others.
2. Cecil was killed during the struggle with the unknown entity during his final recording. The uncovered mirror trapped his soul, trapping him in this world, as his mother, who knew what was coming, had tried to prevent. Cecil is a ghost without realising it. This is why Cecil's previous memories are fading other time, and why his family 'left'. if was never them that 'left'. It was Cecil himself.
3. The 'Cecil' from these recordings is the Cecil from the alternate universe we saw in a previous episode. Their souls were swapped following the 'attack'. This is why alternate-universe-Cecil sounds much more similar to the Cecil from the recordings, and why both men are both so disturbed by the others photo, 'our' Cecil describing the other Cecil's photo appearance as 'evil'.
4. Or, much more simply, a brainwashing, memory removal/manipulation process was a mandatory part of Cecil's induction process in to his job.
I'm probably completely off the mark, but these are my personal thoughts.