Lipa has always refused to accept her place as a girl nutria in the rigid society of her burrow. She is fiercely protective of her brother, Suho, a runt who claims to understand the signs the humans have posted along the riverbanks. He believes that their river rat colony is about to be exterminated, but his warning is dismissed by the nutria leaders, who cling to their traditional mythology. The brother and sister decide to run for their lives...