A typical day in the life of Ivor the Engine. Ivor delivers Coal to Grumbly Gasworks, tomatoes to Mr Davy and Fish to Mrs Thomas. Ivor also goes to choir practice.

Going past Smoke Hill, an extinct volcano, Jones and Ivor spot smoke coming from the top. Jones discovers a fire inside the hill and a strange egg. He puts it in Ivor's firebox to keep it warm.

Dai Station isn't too pleased about Ivor's new friend, Idris, travelling in his firebox. He orders him into a box, which catches fire and then scares him off trying to extinguish it. So where has Idris got to?

After choir practice Idris helps out Mrs. Thomas, whose fish fryer is on the blink. While everyone is enjoying a fish supper, Evans the Song spots a worrying article in his bit of newspaper.

Idris is still missing when the representative of the antiquarian society arrives to interview Jones about him. After a few embarrassments, Jones and Ivor find Idris in the most obvious place.