It's a LOT different of a film. Find it on IMDB/RT to read about it.
Basically, he's a really introverted kind of socially stilted guy who lives in the midwest who starts having horrible dreams about storms/tornados threatening his home and family, and so he starts getting obsessive to the point he has trouble working and starts digging up the backyard to put in what seems to everyone else like a needless storm cellar. (like Noah in the Bible -- "the apocalypse is coming" but everything thinks he's crazy.) It's that kind of psychological and personal drama, where all the other people are reacting to him in different ways, and he's so sure of his visions which torment him, but he's also acting obsessively. His wife I think is played by Jessica Chastain.
A lot of the role is internal, but Shannon still finds ways to express it. It's kind of agonizing to watch. It's handled in a very "believable" fashion, and it's hard to tell whether he's a man who has been cursed with an authentic vision or is slowly going mad while his wife is trying to figure out how to help him AND protect the kids.
http://www.imdb.com/title/tt1675192/
EDIT: It's one of those films that barely makes anything in the theater (budgeted at $5 million, brought in around $2 million in US theaters), but won a buttload of indie-style awards for the movie and/or for the two leads.