A San Francisco-based scientist, Will Rodman, is determined to find a cure for Alzheimer's disease by testing a new drug named ALZ-112 on chimpanzees. The drug appears to significantly boost intelligence in the test subjects, notably a chimp named Caesar, who inherits these heightened abilities from his mother who had been given the drug during pregnancy. After a tragic mishap in the lab, Will takes baby Caesar home to prevent him from being euthanized. Over the years, Caesar displays exceptional cognitive skills, comparable to a human child's. Will becomes deeply attached to Caesar, raising him alongside his dementia-stricken father, Charles, whose condition briefly improves with secret doses of the drug.

Caesar's life drastically changes as he matures. A violent incident leads to his incarceration in an ape sanctuary, where he suffers abuse at the hands of the staff. Amidst the harsh treatment and social struggles with other apes, Caesar's intelligence continues to grow, leading him to recognize the vast differences between ape and human worlds. His experiences at the sanctuary sow the seeds of discontent and the desire for freedom, not just for himself, but for all apes. As Caesar's revolutionary instincts awaken, the balance between species begins to tip, setting the stage for a seismic shift in the hierarchy of Earth's primates.