A Fool and his Honey ~ Charliane Harris

This is the sixth book in the Aurora Teagarden series. One day, out of the blue, a young woman turns up on Aurora's doorstep, with a baby, as it turns out, this is Aurora's niece, with a baby that no one knew she was having. Aurora and Martin have a previous engagement that evening, but set up the niece in the apartment over the garage. Only to return later that evening to find the niece gone, her husband murdered on the stairs to the apartment, and the baby sleeping contentedly under the bed. Now Aurora must care for the baby while trying to solve the disappearance of her niece, and the mystery of why no one had any clue there was a baby involved.