Just caught this by accident. A genuinely unsettling movie, with a twisty time-travel story that gets weirder and weirder - and weirder. Won’t spoil at this stage, but I highly recommend it if you’re looking for something fresh and un-cliched.
The overall feel is like an extended episode of the original Twilight Zone - i.e. it’s intense and narrowly focussed on one powerful s-f theme and a few characters, almost to the point of claustrophobia (and in fact, although you’ll probably guess it all about a third of the way through, going through the motions, with a growing sense of fascination and creeping horror is still worth it, and fits the theme … ). The fact that it’s based on a Robert Heinlein story sort of adds to the Twilight-Zone-ishness of it, it has that solid feel of classic, mind-expanding s-f.
Nice period settings from the 40s, 60s, 70s and 80s, great acting turns from Ethan Hawke, good old Noah Taylor and an amazing Sarah Snook.