Sandcastle. Vintage Classics Murdoch Series, Paperback/Iris Murdoch

The quiet life of schoolmaster Bill Mor and his wife Nan is disturbed when a young woman, Rain Carter, arrives at the school to paint the portrait of the headmaster. Mor, hoping to enter politics, becomes aware of new desires and a different dream of life. Mor's teenage children and their mother fight discreetly and ruthlessly against the invader.