SPOILER ALERT SPOILER ALERT
Okay, now that you have been warned, I will explain to you the plot. It's so sad that so few people seem to be able to follow a complicated plot these days-- the old crime thrillers thrived on the audience being able to follow something that is not spelled out for them, but that skill is lost these days. Even after this movie completely spelled out what is going on.
This is what happens in the plot of the movie, in time order:
A young man, John, is happily married with a kid son. Then he goes off to war in Iraq and is killed. His wife remarries a local construction kingpin, who becomes abusive to both the woman and her son. Her son is brilliant and hides away in his room every day programming his computer. He eventually creates a computer game about fishing (in remembrance of a great memory of fishing with his father) and populates the game with artificial intelligences (AI). The program is so good that these AIs become self-aware and think they are real people living in a real world (like the Matrix, or the Truman Show, or The Sixth Sense, the main character doesn't know what the real deal is until the end).
Eventually this kid becomes so disturbed at the violence of his father that he changes the game and inserts AI versions of his mom and his stepdad into the program, and then has the mom try to bribe the real dad (the AI dad in the program) to kill the AI stepdad. The greatly disturbed the operating system of the game, which is also self aware (represented in the program by a dorky guy with a briefcase). It tries to contact the AI version of the dad and convince him not to kill the stepdad, and instead to return to the original mission of catching a fish, and also tries to put road blocks in his way. The AI dad (the main character) forces out of the operating system AI the truth that they are all AI consciousnesses, not in the real world. Although he struggles to accept this, he decides to go ahead and perform the new mission of the son, to kill the stepdad, since the son is his creator. He eventually convinces the operating system to embrace this cause too, since after all they are all just doing the will of their creator.
So they succeed at killing the AI stepdad, and this inspires the kid to go kill his stepdad in the real world. In the end, the kid is in jail but has access to his computer, and he designs an AI version of himself and inserts it into the game, and the movie closes with him embracing his (dead, but now AI) dad. Perhaps they will live happily, or only until someone switches off the computer.
So many fascinating philosophical issues involved. If you realize you are an AI, and the creator is not a good and just creator but a messed up kid, are you duty bound to do the will of your creator? Or is there a higher law that binds you to do the right thing, even above the kid-creator? One of the AIs in the game, the second mate of the ship, argues that they must be faithful to a higher moral call-- but argues this on the basis that there is a creator. But he doesn't know the creator of their world is a messed up kid, not omnipotent. Could it be that he knows somehow in his heart that there is an even higher creator than the kid, a true Creator of the world that contains the kid? After all, the kid lives in the real world and knows about religion. Another question: does the AI dad have free will? Is he responsible for the kid in the real world committing murder? Or did the kid program him to do his will, without a choice? The movie seems to indicate that the kid was waiting to see what his AI-dad would do before making his own decision.
Some reviewers have complained that the opening of the movie is cartoonish--the AI dad is clearly cartoonishly copying the plot of Moby Dick; the AI mom is a caricature of a film noir vamp. But that is because they are the cartoonish creations of a 12-year-old! That's the point-- the whole "world" is a Matrix-like world, the creation of a smart but emotionally crippled child. The really interesting thing to ponder is what if you realized one day you were in that Matrix world.
This type of "what is real?" movie and "would I know the world was a mirage?" has become a genre, including the Matrix, the Sixth Sense, and the Truman Show. One could also put the old movies Gaslight and Walter Mitty (not the recent version) in this category. Serenity, the Matrix, and the Truman Show all ask the question, what if the creator isn't good? In the Matrix and the Truman Show, the main character fights against the creator (who, after all, is not the total Creator but only a sub-creator of a limited world), while in this movie the main character acquiesces to the will of the (deranged) creator of his world. There is an odd meta-nesting: he recognizes that he isn't real, but realizes that there was a real dad who loved his kid before he died, and he takes pity on the kid, trying to parent him by becoming what that real dad could have been-- even though the kid is his creator.
So fascinating. Too bad that so many people couldn't follow it. It will be discussed in philosophy classes for years to come.