Socks, the black brumby with four white legs, is a loner until one day he hears the bronze cuckoo whistle and the cattle dog follows him into the bush. They become great friends, the dog Lightning, whose master has died, and the horse. The bronze cuckoo keeps an eye on them when parties of men with whips and dogs come into the area to capture the brumby herds and take them to the sales. A female dingo joins Socks and Lightning and soon there are pups to take care of as well.
Although not many men go deep into the Snowy Mountains, the bushwalkers carry strange tales of a black brumby and a family of dogs and dingoes. The stockmen are always curious about these tales, especially when the brumby and the dog keep eluding them. The confrontation is fierce when it comes and the animals escape ... but for how long?