A teenage girl whose brother is lost at sea...the diary of a nineteenth-century woman...and the special place that binds them.Lisa Duncan, a seventeen-year-old high school senior, has an assignment to tour historic Mirabelle Manor, a large estate built in 1850 by a sea captain for his wife. During the tour, she begins to suspect that Mirabelle's ghost is watching her. One of the items on display is a diary, open to a passage about going to a place called the unicorn tree to watch for ships. This appeals to Lisa whose brother is currently sailing across the Atlantic on a commemorative voyage. When news arrives that his ship is lost at sea, her interest in the diary deepens as the past and present lead her to discover what happened.