Graham Merrill passes a pet shop on his daily walks about London, and takes an interest in an
otter (specifically, a male
river otter) he sees in the shop window; eventually, he buys the animal and names him Mijbil or "Mij" for short. The otter wreaks havoc in his small flat, and together they leave London for a rustic cottage overlooking the sea on the west coast of Scotland. There they live as beachcombers, and make the acquaintance of Dr. Mary MacKenzie from the nearby village, and her dog Johnny. Mij and Johnny play in the water and bound across the fields together. One episode involves Graham trying to find live eels for Mij, which is very difficult because during the winter the eels swim in deeper waters, making it tough to fish them out. Also, no fishmonger in town carries live eels. Mij's inquisitive and adventurous nature leads him some distance from the cottage to a female otter with whom he spends the day. Ignorant of danger, he is caught in a net and nearly killed. The humans find him and help him recover. Graham spends a significant amount of time drawing Mij, but realises that to show the true agility of the otter he must draw it underwater. He builds a large tank out of old windows so that he can do this. Not long after, Merrill goes to London to look after some affairs and leaves MacKenzie in charge of Mij. While being exercised afield, Mij is killed by a ditch digger, who did not realise he was a pet. Merrill returns and is crushed to discover the death of his beloved otter. Some time later, Merrill and MacKenzie are surprised by a trio of otter youngsters, accompanied by their mother otter, approaching the cottage. He happily realises they are Mij's mate and their children who have come to play in their father's swimming pool. Graham has been trying for years to write a novel about the
Marsh Arabs; however, after seeing the baby otters playing, he takes pen and paper and begins to write about Mij and what the otter has taught him about himself. ==Cast and characters==