Zathura is a movie that begins with three siblings Walter (Josh Hutcherson), Danny (Jonah Bobo), and Lisa (Kristen Stewart). These siblings are constantly fighting with one another and on this particular day none of them can get along. To make matters worse they are all stuck inside while their father is at work. Walter and Danny find an old game at their father's house. Having nothing else to do they decide to play the game. Their sister becomes an unknowing participant of the game. The main goal of the game is to get through space and get back home. Just thinking that it is a regular game, the boys roll the dice. To their amazement they are no longer on Earth, but floating through space.
One of the cards brings Zorgons that invade their home. Another card brings an astronaut (Dax Shepard) who has been stuck in the game for a long time. Together with the astronaut, the brothers thwart an attack from the Zorgons by making the house cold. Danny tries to cheat the game, but Walter is punished by being sucked out into space. Walter is awarded with a card because Danny tried to cheat the game. Walter really wants to wish for his brother to disappear, but the astronaut talks him out of it by telling his own story about the game.
The boys make the decision to finally end the game. Not knowing what is going on, Lisa who is cold, turns up the thermostat and the Zorgons return. They quickly run up to the second floor only to realize that they forgot the game. Together all of them come up with a plan; Danny will use the dumbwaiter to go down and get the game. Walter uses a robot to fight off the Zorgons and reclaim their home. Walter gets another wish card and uses it. This reveals that the astronaut is an older version of Walter.
The Zorgons come back with reinforcements determined to take over the house. The boys realize that they must finish the game. Danny gets to the final space and a black hole emerges from the game engulfing everything in sight. Just when all is lost, the kids realize they are back on Earth.