This is one of those shows I wish I could have heard in the original broadcast. It would have creeped me out totally. Not the UFO tie-in but the psychological aspects and especially the sound beds. The child's voice was disturbing and not something that occurred much in RMT. Unlike the usual haunts, ghost voices etc., the sound of an emotionally traumatized child has a troubling aspect that a classic gothic horror ghost voice doesn't have.
I don't think I can grasp the psychological aspects entirely, I don't know how Arl came to appear to Robbie in the first place but I figure what transpired after that was due to the beating. If it was in fact the first time the father hit his son, and did it "over and over again", then the rest would follow. I also remember thinking, does he really want a discredited lush of a psychiatrist hypnotizing him and bringing this stuff out? Seems the discrediting was warranted, as this guy didn't know enough not to laugh off Robbie's innermost traumas as figments of his childhood imagination. Arling might represent the progression of the emotional disorders beyond childhood, when the imaginary friend becomes a sexual fantasy.
I'm just thinking out loud here and looking forward to reading the posts. This is a great show, I know some people who aren't fans who may well become fans upon hearing it.