Theodore is a lonely man in the final stages of his divorce. When he's not working as a letter writer, his down time is spent playing video games and occasionally hanging out with friends. He decides to purchase the new OS1, which is advertised as the world's first artificially intelligent operating system, "It's not just an operating system, it's a consciousness," the ad states.
For newlyweds Carl and Molly Peterson, life can't get any sweeter as they begin anew to settle down into married life. With a nice house and established careers in tow, nothing seems to get in their way. However, Carl is about find out just how much friendship means when Dupree, his best friend has been displaced from his home and fired from his job because of attending their wedding. Taking his friend in, what Carl and Molly are about to experience is that the fine line between a few days and whatever else is after, can be a lot more than they bargained for. Especially when their friend overstays his welcome in far too many ways than he should.