It’s a remake of a Thai movie that frankly shouldn’t have been remade but marketed to the American public as is, I guess we are too lazy to read subtitles.
Cliff Notes version without spoiling: Guy and girl get in a wreck on the way home. Bad things start happening to friends and he starts seeing weird stuff especially in his photography (his trade). Neck problems seem to creep up on him the whole movie and a ghost starts warning the girl. People die, ghosts haunt, carnage of peoples lives ensues.