It all began with the television outside broadcast featuring Punchbowl Farm and in particular Dion, the boy farmer. Within a matter of days the Thornton family found themselves acting as temporary guardians of a prize Jersey cow. It is soon obvious that there is a mystery attached to the cow. Where has she come from? Who is the strange ‘Mr Drydon’ who brought her to the farm? Events build up to an exciting climax in which the children are involved in a cross-country chase and a strictly illegal cross-Channel trip, to restore the mulberry cow to her rightful owner.