Plot: Will Rodman (James Franco) is a San Francisco scientist who has been trying to develop a cure for Alzheimer's disease by testing a genetically engineered retrovirus on chimpanzees. The virus mutates the chimpanzees, giving them a human level of intelligence. The most successful subject, a female chimpanzee named Bright Eyes (Terry Notary), goes on a rampage because she believes her baby, to whom she secretly gave birth, is threatened. She is killed after disrupting a board meeting. Will's boss Steven Jacobs (David Oyelowo) orders subordinate Robert Franklin (Tyler Labine) to put all the test chimpanzees down, but he cannot bring himself to kill the chimpanzee's baby, and instead gives him to Will, who names him Caesar (Andy Serkis) and raises him in his house. Caesar has inherited his mother's high intelligence, and learns quickly.
Three years later, Will gives a sample of his cure to his father, Charles (John Lithgow), who is suffering from Alzheimer's disease. At first, his father improves but, five years later, his body's immune system fights off the virus and his dementia returns. In his dementia, Charles gets into his neighbor's car and damages it, angering Hunsiker, the neighbor and an airline pilot (David Hewlett). As he threatens Charles and pushes him down, the onlooking Caesar attacks him. After the incident, Caesar is forced to leave Will's house and is held in a San Bruno primate facility run by John Landon (Brian Cox). The apes are treated cruelly by Landon's son Dodge (Tom Felton) who works as a guard there. Caesar is initially treated poorly by both the staff and the other apes, though he forms a friendship with an intelligent circus orangutan named Maurice (Karin Konoval). When Dodge brings his friends into the facility, one of them gets too close to Caesar's cage and is grabbed by Caesar, who steals his pocket knife, later using it to escape his cell. Caesar then frees a gorilla named Buck (Richard Ridings) and, with his help, gains dominance over the other apes.
