The Crossing may have ended last night, if no network or streaming service gives it continuing life, which it eminently deserves, seeing as how these last two episodes redeemed or proved The Crossing's mettle as a time-travel narrative worth watching and continuing, with a classic time-travel slap-in-your-face turn of events. (Spoilers follow.)
The twist was a variant of the perennial time-travel gambit of the trip to the past causing the very evil that the trip was supposed to prevent or at least avoid in the first place. The vehicle in this case was Sophie, who injects herself with some concoction that makes her the first Apex to arise. Reece, who was the first Apex to arrive in our time — that's why I said "arise" regarding Sophie — tries her best to prevent this from happening, explaining to Sophie that Reece doesn't want Sophie to be the start of Apex (but see the following paragraph). But Reece understandably is a bit distracted, still focusing on finding Leah, and still suffering some of the residual effects of her medical torture. So Sophie tricks her.
But Reece may have been distracted about something a little deeper regarding Sophie and Apex. Were Apex never to ever arise, that would mean that Reece would cease to exist. This would mean that either Leah wouldn't exist either (since who knows what effect Apex had on Leah's parents or grandparents meeting), or if she did exist, who knows what kind of life she would have had without Reece and Apex. Maybe Reece was willing to gamble that Leah would exist and be happy without Apex or Reece, but, if this was Reece's thinking, it should have been made more apparent. Not making this clear leaves us with other possibilities, such as Apex being not as mentally superior as they are physically, or having a blindspot to paradoxes of time travel that some us humans know about right now.
The Crossing, however, deserves credit for pitching us into these questions and quandaries — that's what good time-travel story-telling should be doing. Should not a first season of a series exceed its reach, or what's a second season or meta-for? (Apologies to Robert Browning and Marshall McLuhan). And The Crossing has left us with other compelling questions, such as why was Ellis's name was all over the wall with Apex writing from the future, and why was Marshall's (not McLuhan's) picture in Hannah's locket? (Maybe the picture in the locket was earlier explained, though, and I missed it because I got too tangled up in the paradoxes.)
Not to mention that Homeland Security's treatment of the immigrants from the future in The Crossing bears disturbing resemblances to Homeland Security's treatment of immigrants from south of the border — the geographical not temporal border — right here in our reality. (Is that why the series wasn't renewed? Who can say?)
Here's something I can tell you for sure about one possible future: if The Crossing continues somewhere, I'll be sure to review it. If not — well, I enjoyed this first season, especially the past two hours.