The Owl Service Bande son (1969) BO

Recently bereaved teenager Alison goes with her step brother to stay for the summer in the quiet retreat of a relatives house in the Welsh Valleys. After hearing a scratching noise coming from the roof of the house, Alison discovers some old dinner plates in the attic which have a flowered owl pattern. What is the connection between this, the loony gardener, the angry housekeeper and the legend of the old village magician, who made a wife out of flowers and later turned into an owl when she betrayed him?