As for the plot, it's somewhat murky - as I guess befits afterlife stories - and manages to combine the ambience of grade-B 1950s science fiction/horror, replete with a hokey laboratory, more than reminiscent of the Frankenstein-monster set-up, and the more modern retelling of early events and dialogue in the movie, near the end, in a way which makes the beginning make more sense, though it wasn't all that opaque in the first place.
Redford is the scientist who thinks/claims he has discovered evidence of an afterlife. His son (played by Segel) resists this because it's somehow tied up with the death of his mother. He in turns falls for Mara's character, who has a complex story of her own. I won't tell you more, lest I give too much away. In other words, I'd like to see this movie have an afterlife.
All in all, I'd say the best part about it is the at-once jarring, compelling, and subtly controlled way in which the movie was shot, including a long speechless scene with Rooney on camera, thinking about something, sitting next to Segel on the beach, about to tell him a crucial piece of this story. That kind of pacing is realistic and hard-to-find in science fiction. Kudos to film maker Charlie McDowell.
It started in the hot summer of 1960, when Marilyn Monroe walked off the set of The Misfits and began to hear a haunting song in her head, "Goodbye Norma Jean" ...