The story, taking place in a near future when people spend more time talking to their computers than they do to each other, stars Joaquin Phoenix as Theodore Twombly, a lonely man whose job is to write heartfelt personal letters for people not willing to do it themselves. Theodore happens to see an ad for a new computer operating system that is programmed with a personality, and decides to give it a shot. His new operating system Samantha, voiced by Scarlett Johansson, is not only intelligent but also charming and understanding, and she and Theo quickly fall in love.