A Stranger in the House by Shari Lapena is built around the idea of how well you can really know someone. Tom and Karen Krupp have a seemingly perfect marriage until the night Tom comes home to find Karen missing. She ends up in a terrible accident that night in a bad area of town. Afterward, she has no recollection of why she was there in the first place. Tom is happy that she survived the crash, but now he can’t help but feel uncertainty toward his wife. What was she really doing?
All would end up fine except that a man was murdered during the time frame of Karen’s accident. Most concerning is that there is evidence tying Karen to the murder scene. Tom begins to find out that Karen isn’t exactly who she claimed to be. The murdered man is in fact someone from her past who she would have reason to kill. Tom must come to terms with Karen’s past while also dealing with their odd neighbor Brigid; she is someone Tom has had his own encounters with before meeting Karen.
Brigid hasn’t been completely honest either. She obsessively watches Tom and Karen from her home across the street. She has ulterior motives for wanting Karen to be convicted as a murderer. Ultimately, Karen and Brigid have met their match in each other. Both have unpleasant secrets, they are out for themselves and they are determined not to let anyone get in their way.
There are hints of the movies Single White Female and Sleeping with the Enemy in this book, but there are plenty of differences to keep things interesting.