The Enid Blyton Adventure Series
The Island of Adventure: Part 1
S1 E1:
When they discover their guardian is sick, Jack and Lucy-Ann accept Philip's offer to spend the rest of the holiday at his new cliff top home in Cornwall. There they meet Joe, a friendly man who helps Philip's widowed mother Allison, at her Art Gallery, and Philip's sister, Dinah. But as they leave they are followed by a stranger.