The Ghost in the Walls by Eric Kanin

By anyone's measure, John Callaway is a man with the world at his feet. Married for thirteen years to his high school sweetheart and expecting twins, Callaway is also the founder and CEO of his own specialty pharmaceutical firm, a wildly successful venture that is on the cusp of propelling him to even greater heights of achievement. But on a routine business trip, fate steps in and his carefully crafted world is changed forever.