Shattered Haven by Carol J. Post

Allison Winchester's old Victorian house contains a valuable secret code, one that someone is dead-set on uncovering. After her house is ransacked and her life is threatened, she has no choice but to accept the protection of injured ex-cop Blake Townsend. Allison never thought she'd trust a man with secrets again—and Blake is as much a mystery as the man who is stalking her. The lawman vows to shield her from the dangerous criminal. But can Blake and Allison decipher the mysterious code before their island safe haven becomes their ultimate resting place?