Adventure is triggered off by a telegram. When their father becomes ill in Bangkok, four English children are sent by their mother to stay with Great Aunt Dymphna in Ireland.

Slightly eccentric Great Aunt Dymphna collects the four children and drives them to her old, derelict house.

The children hide a foreigner named Stephan in the house. Stephan explains that he is a foreigner on the run from his father’s political enemies.

Penny and Naomi become alarmed when their aunt and the boys fail to return from a fishing trip.

The mystery of Stephen’s identity has been solved. Intrigued by Stephen's predicament, the children follow a trail that leads them to the basement. However, they eventually realize that the clue and the blood they found were fake. They decide to report their findings to Miss Oonagh. Upon investigation, she discovers that Stephen is not a stranger, but rather a young movie star trying to escape from school. Miss Oonagh then hands Stephen over to the police. With him gone, the children's lives become much simpler. The only issue remaining is their father's illness, about which they have received no updates.

In the final episode of this six-part children’s adventure serial, the children hear that their father’s health has improved and that they can go home to London. They suddenly realise how much they will miss their unconventional Aunt Dymphna (Wendy Hiller) and decide to give her a present. Unsentimental to the last, she fills their remaining time with activity, and leaves them at the airport as suddenly as she came . . .