The House of Lost Horizons #1

Sarah and Marie-Therese travel to a secluded island at the request of Sarah's old friend Lilian Whetstone, to help with the appraisal of Lilian's late husband's artifacts. On their arrival, they learn that Lilian's attorney died mysteriously the night before. As they begin to investigate, questioning the several bidders for the items who have gathered, another similar death takes place.