House of Shade
Other title: Death in Zanzibar. From the fantastic fiction webpage: "Dany Ashton is invited to vacation at her stepfather's house in Zanzibar, but even before her airplane takes off there is a stolen passport, a midnight intruder--and murder. In Zanizbar, the family house is Kivulimi, the mysterious "House of Shade", where Dany and the rest of the guests learn that one of them is a desperate killer. The air of freedom and nonchalance that opened the house party fades into growing terror, as the threat of futher violence flowers in the scented air of Zanzibar. Richly evocative, Death in Zanzibar will charm long-time fans and introduce new ones to this celebrated writer."