Acorna's Search, the fifth book in Anne McCaffrey's Acorna series, takes the saga of the beloved unicorn girl to an all-time high -- or low, depending on how you look at it. As Acorna and her Linyaari people begin to rebuild their home planet (which was practically destroyed by the evil insectoid Khleevi in Acorna's World), members of Linyaarian research parties begin to disappear one by one. Soon whole shuttles are just vanishing into thin air. Among the missing is Acorna's life mate, Aari. After consulting with the Ancestors, Acorna concludes that she must go deep underneath the planet's surface to solve the potentially horrific mystery.