A pet-shop otter changes a man's life when he feels compelled to move it to the Scottish coast.

Graham Merrill, a London clerk for the civil service, has become increasingly dissatisfied with both his computerized job and automated society in general. While passing a pet shop one day, he catches the attention of a caged otter on display in the window; as he continues his daily walks by the store, Merrill gradually comes to believe the animal has singled him out from all the other pedestrians. He overhears two show promoters discussing the otter and decides to purchase it himself, but soon realizes his urban apartment is too small to house the rambunctious pet. When the otter's playfulness causes his landlady to evict him, Merrill buys a small cottage in the Argyllshire area of the Scottish highlands, where he plans to write a book on Arabian culture. Most of his working hours, however, are spent with the animal, which he nicknames "Mij"; in addition, the two of them enjoy the company of an attractive doctor, Mary MacKenzie, and her pet spaniel. One day, Mij runs away with a female otter, and is later found in a fishing net on a nearby island, badly injured and nearly drowned. After nursing the animal back to health, Merrill is called back to London. Mary agrees to care for Mij, but a road worker accidentally kills the pet during the writer's absence. Merrill returns and, upon hearing the news, becomes too distraught to work, until a female otter and three cubs suddenly appear at Mij's favorite watering spot. Inspired by the realization that they must be Mij's family, Merrill begins writing about otters.