The gunman was very well written, but the actor wasn't powerful enough for the part, perhaps? I know the point was that he was a grey faceless man, but he could have been more disturbing. Without changing the script he could have been a more convincing 'man out of time', perhaps Sam's blood brother. That would have made the urgency or saving his life, and the parallel with Sam's own redemption, more marked.
In terms of 'what is really going on' Abigail rightly says that making Sam actually mad, a madman in 1973 who coincidentally (or from precognition or something) has tuned into the modus operandi of the 21st century, or an idealised form of it, would be a disturbing resolution. Too disturbing for a mainstream show probably. And for exactly that reason I would like to see it given more weight, and for it to occur to more people.
Ideally I would like the show to maintain its ambiguity, but not by losing interest in resolution, not by merely turning into a fish out of water cop show and/or amusing parody of old-style cop shows. Instead I would like the show to emulate Doctor Who by attempting to swim about in murky psychological waters. What if you were working with a madman. What if you were a madman? What if - and I think this is the essential question - there was no difference between being unstuck in time and unstuck in mind, and unstuck in story? What if there was no clear dividing line between characters in your head, who just represent suppressed aspects of yourself, and people in the past, and people on the telly?
Yes, that's all I want. All the major issues of SF and modern angst, in an hour a week. Thanks.