Fiction by Patricia MacDonald.
This story starts out with a convenience-store robbery and then shifts to a woman babysitting her preschool-aged grandson while the child's parents go on a cruise for a much-needed break. Almost immediately the second storyline becomes absorbing enough for the reader to forget the first, until they intersect once again... But the connection is not quite what you think.
This was an exciting thriller!
I also read recently by this author: Stolen in the Night