Pauline, Petrova and Posy are found as orphaned babies in different parts of the world by eccentric fossil collector and explorer Gum. He adopts them, takes them to his London home and leaves them in the care of his niece Sylvia and the family Nurse. Then off he goes to continue his exploring, saying that he'll be back in five years' time. When the three little girls are old enough, they choose the surname Fossil for themselves and vow to make the name famous.
At first they lead privileged and sheltered lives. But when Gum fails to return after five years, Sylvia's money begins to run out. First she is forced to take in some boarders - an engaging and eclectic mix of characters - but then she decides that the girls should go to acting school. This way they will be able to earn some money before they grow up.
Pauline adores the school, as she dreams of becoming an actress. Petrova hates it, all she wants to do is learn about cars and planes and engines. Posy loves it too - she is born to be a dancer and the school is the perfect place for her.