The Ruby Locket — Anita Higman

When Anne's mother agrees to marry a wealthy, mysterious man, she expects a nice mansion in the hills. But their new home, Belrose Abbey, is more like a castle -- imposing, cold, and full of shadows. The more Anne explores the corridors and vacant rooms and dusty crannies, the more she discovers about the abbey's master -- her soon-to-be stepfather -- Ivan Helsburg. As her mother's wedding draws closer, Anne begins to harbor a creeping suspicion that all is not well at Belrose Abbey.