S1, E1: Documentary following ultimate cat species from around the world, from the lions of Tanzania - the only cat species to live in groups - to the tiny rusty spotted cat of Sri Lanka, 200 times smaller than a lion but just as curious. The film also peeks into the secret lives of the Canada lynx, which lives further north than any cat, and follows an African leopard and mother, which for a decade has worn a radio collar allowing scientists to follow every twist and turn of her existence.