The plot concerns the theft of wild cattle from a Scottish borders castle, and their recovery by children helped by friendly ghosts.

Madlyn is helpful to her brother and mother, who is usually frantic and forgets things like car keys.

At the beginning of the summer term, Mr Hamilton receives a large offer from an American college (which the family needs) to spend two months in New York setting up a business course in design.

The parents cannot take the children but decide to go to America, sending Madlyn and Rollo to stay with their Uncle George and Aunt Emily (sister and brother) at Clawstone Castle on the Scottish border.

Mrs Grove's sister comes to start taking the tickets, bringing with her what the villagers have donated to help the castle.

Then Madlyn meets Mrs Grove's son, Ned, and learns about Olive, the Trembellow's daughter.

Brenda the bloodstained bride, Mr Smith the skeleton, Sir Ranoulf the man with a rat in his chest, Sunita the sawn-in-half girl, and a pair of disembodied feet all help to make the castle popular with tourists.