First Broadcast on 18th September 1978
Executive Producer James Gatwood
Produced by Don Leaver
Directed by Don Leaver
Adapted by Richard Sparks
Guest starring:
Michael Hinz, Sue Best, Ray Armstrong, Gertan Klauber, Diana Lambert, Peter Wilson, Paul Stacey & Jeremy Stacey.
George and Anne are away camping and encounter a boy named Guy, the son of a famous archaeologist named Sir John Lawdler, and his small, one-eyed mongrel dog called Jet. The boy is excavating an old Roman camp to search for artefacts and asks the girls not to disturb him.
Later that day, the boy's twin brother named Harry (which is later revealed) comes to the area, but the girls mistake him for the first boy and are confused .
That night it starts raining and the girls take shelter in an old ruined cottage. anne wakes up in the middle of the night disturbed by thunder and sees three strange men outside, which she thinks are ghosts.
The next day, Julian and Dick arrive the next day and notices the Anne and George are about to leave, the girls say about their reason for leaving the camp. Later, the four children decide to stay in the ruined cottage to see what would happen. That night, while sleeping in the old cottage they hear weeping and wailing noises and see some kind of light that makes them a bit afraid. The next morning, the four understands that someone was trying to get rid of them from the old cottage.
Julian and Dick decide to visit the old cottage that night, to find if there were any suspicious activity going on. They find that a gang of people are trying to find a secret tunnel in which a very precious blueprint was kept. The boys then declare their findings to the girls. Later George finds a clue to the secret tunnel where they discover a leather bag, that felt very light and when opened the bag is empty. They then trap the thieves in the tunnel.
The police tear the lining of the bag and find a blueprint, which Uncle Quentin reveals is a secret document which has only two copies in the world, one with himself and the other with Sir James Lawton-Harrison (which has been stolen). The Police arrange for the document to be returned.