The Darkest Evening of the Year by Dean Koontz

Amy is an animal lover who rescues Golden Retrievers from abusive homes.  But Amy has a secret, a hidden past where she used to be someone else, and that past is creeping up.  While she is away caring for Nicky, her newest Golden that she also decided to keep, a man carefully goes through her house-- searching everything, looking for clues that might tell him who she really is.  Over the years Koontz has written more and more about dogs (specifically Golden Retrievers), and this book is perhaps the most dog-specific book of his I've read to date.  This is part suspense, part dog-rescue manifesto.  It's not the gripping suspense of Koontz's earlier works, but there is enough to make it an enjoyable story (and to make you want to curl up with a Golden!) The title is taken from the Robert Frost poem Stopping By Woods on a Snowy Evening.