At the critical moment in the story, when German Mailer is about to kill Herdeg, Herdeg fatally shoots Mailer's father, Mahler. Mahler dies surprisingly quickly, and Mailer is startled by this. Then, more than startled, Mailer is destroyed, undone, as his body dissolves into the vortex. A wounded Dave drags himself the last few yards and stretches one hand into the field, and is then sucked into the future.
How does any of this make any sense at all?
We are supposed to conclude that because Mahler died childless, Mailer was never born, and because Mailer was never born he cannot now exist. Thus his existence ceases, and he is not there. Yet he was there, and his existence is the direct cause of the injury in Dave's arm and of the temporal gate that awaits him a few feet away. If Mailer now never existed, then he never existed five minutes ago, never came through the portal, never created the portal, never did anything he has done in the movie. So what would really happen?
The problem is the more complicated by the mistakes already made. If American Mailer accidentally sent a stealth bomber to Weisbaden, 1943, changing history such that Germany bombed Washington and won the war, then in 1993 there is no stealth bomber and no teleporter program by means of which to send it to the past; we covered this already, but it complicates our situation now. The stealth bomber now is as much "never born" as Mailer. The only plausible resolution is that somehow Niven's Law means that once the past has been changed it remains changed unless someone from the future changes it; that is, once the bomber has come to the past, it exists in the past even if its creation in the future and trip to the past are undone. Yet if that is so, then it applies equally to Mailer: once he has come to the past, he exists in the past even if his actions cause him to cease to have come into existence in the future. While this resolves the problem of the Grandfather Paradox, it is not what happens in the film.
If we ignore the problem created by the bomber and assume that somehow Mahler obtained the bomber and used it to win the war, and if we ignore the problems related to Dave's presence in 1993, we reach yet another infinity loop. This, though, may be one of the most complicated looping sawtooth snaps represented in any film, even once we eliminate the intervening infinity loops. We will set it aside to address next time.
Meanwhile, if German Mailer does not instantly cease to exist, he should be able to kill Herdeg and return to the portal himself, to be transported back to 1993, arriving in yet a different future in which America won the war but he was born in the NAZI German empire that never existed. Of course, time ends at that point--for the same reasons that this Dave Herdeg cannot be in that universe, that Friedreich Mailer cannot be in this one. But with that much to consider, we will look at the complications in our next installment.