This was even worse than the later "The Returned" TV series. While the theme of the TV series is that of the "existential crisis," They Came Back is an allegory for immigration. Yet, at the same time, the producers attempt to show how the "real world" would handle such an event as the reappearance of the dead, and how such people would be reintegrated into society. However, like the TV series, the producers seem to forget that the most realistic, obvious course of action would be to excavate a grave or two in order to check the veracity of somebody's claim that they are who they say they are. It's such an obvious miss on the part of the writers/producers that it is unforgivable. (Seriously, wouldn't that be the VERY first thing that would come to mind? It was for me . . .)
So, unless you like slow, brooding material that bangs you over the head over and over again with its theme, while simultaneously botching the surface story, then look elsewhere for entertainment. Let's hope that ABC's new "Resurrection" fares better.