The Shivering Sands by Victoria Holt.
Roma and Caroline Brandon's parents were both archeologists. Their parents were keen for their children to follow in the footsteps but only one decided on this course. Roma became well known in the field of archeology and in particular excavating Roman remains. Caroline chose a more 'sedate' lifestyle; she became a concert pianist and although not one of the worlds greatest pianists herself, she married a famous musician.
Her married life was far from bliss but when her husband Pietro unexpectedly dies her world is shattered and she is consoled by her sister.
On the south coast Roma was excavating a Roman village near Lovat Stacy ,a fine country house. After Caroline's departure Roma disappears. In need of employment Caroline finds a position in the country house as a piano teacher. Here she hopes to solve the mystery of her sister's disappearance .The members of the Stacy family prove to be a complicated and suspicious bunch , and many appear to regret Caroline's presence.
'A feeling of claustrophobia came to me ; she would keep grasping my arm, putting her grotesque little girl face close to mine... and I was in agreement with those that said she was not all there.'
'There is a light in the chapel. That's not imagination...'
'It's an eerie place. Besides it's trespassing and if people were trespassing they wouldn't show lights to betray themselves, would they?'
In discovering the reason for her sister's disappearance, one of her pupils vanishes.Caroline now fears that her own life is in danger, she needs help, but can she trust any member of the Stacy family?
Another good read from Miss Holt. Full of suspense and excitement. Highly recommended.