Killing Time — Linda Howard

In 1985, a time capsule was buried under the front lawn of a small-town county courthouse, to be reopened in 2085. But just twenty years later, in the dead of night, the capsule is dug up and its contents stolen. That same night, one of the contributors to the capsule is brutally slain in his home--with no sign of forced entry or indication of struggle. One by one, others who had placed items in the time capsule are murdered. Besides his suspicions about the sudden, mysterious appearance of Nikita Stover, chief investigator Knox Davis has absolutely no leads. The smart-talking Nikita may be no murderer, but she seems to be hiding plenty of secrets. With more at stake than anyone else realizes, Nikita is determined to catch this cunning killer--while at the same time battling her own deepening feelings for a man and for a world in which she doesn't belong.