Locusts, bees, birds, and other creatures that move as one are the subject of this two-part documentary, which uses close-focus and slow-motion camera work to get inside a swarm rather than just watching one from a distance. The footage tries to approximate how these animals sense their surroundings, tracking the chain reactions of movement that let thousands of individuals turn, scatter, or converge as though sharing one mind. Alongside the wildlife photography, the film pulls in footage shot by ordinary people on camcorders and mobile phones, capturing moments when swarms crossed into human territory: birds blackening a sky over a town, insects overwhelming a building or a crowd. That amateur footage does something the nature photography can't, showing swarms as a lived nuisance or hazard rather than a spectacle. The two episodes move between the biology of why animals swarm and the practical disruption it causes when nature's crowd control breaks down near people.