The story, 'Mijbil the Otter' begins with the writer, Gavin Maxwell who is travelling to Basra with his friend to the Consulate-General to collect and answer their mail from Europe. During their journey, Maxwell expresses his desire to keep an otter as a pet instead of a dog as he feels very lonely after losing his pet dog earlier. His friend suggests that he get an otter from the Tigris marshes in Iraq. When they reach the destination his friend receives the mail immediately, while Maxwell has to wait for a few more days to receive his mail. Once he receives the mail, he takes the sack that was brought by two Arabs carrying a message from his friend and discovers an otter inside it. He christens the otter Mijbil and often refers to it as Mij.
It takes a little while for the little creature to adapt to its surroundings. In due course, Maxwell observes that Mij enjoys playing with water and he even learns to open the bathroom faucet on his own. The writer is thoroughly amazed by the games played by Mij with his own touch of creativity. Soon the time comes for Maxwell to return to England with his pet otter. However, the British Airlines had a few restrictions that barred animals from travelling with human beings, so he books another flight that allows Mij to travel with him. The new airlines insist that Mij should be packed in a box so that he doesn't disturb other co-passengers onboard. Hence, Maxwell arranges a box one hour before the flight, puts Mijbil inside, and goes to have a quick meal.
When he returns, he finds there are holes in the box and the edges are stained in blood. He understands that Mij must have injured himself inside the box. He cleans the box properly and reaches the airport a few minutes before the flight takes off. When he boards the flight, he explains the entire incident to an air hostess who advises him to keep his pet on his lap, rather than locking it inside the container. Maxwell is filled with gratitude for her kind words. But the moment he opens the box, Mij leaps out and vanishes in thin air that causes a lot of chaos in the flight. Many co-passengers get astonished seeing the little creature moving around. Eventually, Mij finds his way back to Maxwell on the flight, and finally, they reach London. In London, Mij gets used to his surroundings gradually. He starts playing with marbles and ping-pong balls. The writer is also amazed at the game that Mij had developed with his broken suitcase. Maxwell often takes Mij for a walk and the people of London make wild guesses about his pet. They refer to Mij as a baby seal, beaver, squirrel and there are still a few more who refer to the otter as a hippo. The most shocking response that Maxwell receives is from a labourer who on seeing Mij asks the author, "Here, Mister what is that supposed to be?"
The story Mijbil the Otter, explains the beautiful bond of the author with his pet otter, Mijbil, and describes the series of incidents that followed during their onward journey to London and later.