Firefly — R.W. Clinger

Cookbook designer Bay Woods begins to notice strange things happening at his lake house. He could swear someone is visiting his gardens at night, leaving the wrought-iron gate open. And some of his clothes are missing, too. He soon realizes there might be a trespasser in the quiet neighborhood, and maybe something even more mysterious.

As summer stretches on, Bay notices an unusual number of fireflies every evening. One in particular seems to follow him around the property. Why exactly?

Then Bay learns his trespasser is the tall and handsome Christopher Lavre. Unsettling questions make him what Christopher's link is to the fireflies at night. Or rather, one lightning bug in particular...