David Attenborough explores the fascinating world of monkeys, revealing surprising parallels with human behavior. Examining everything from memory and morality to social dynamics and politics, the film highlights how monkeys offer insights into our own origins. We see pygmy marmosets cleverly gathering food, capuchins in Brazil employing a sophisticated system for processing nuts, and Costa Rican monkeys displaying compassion towards injured others. Meanwhile, a lonely baboon in Ethiopia grapples with personal sorrow.