"The Underdogs" explores the world of service dogs, which has expanded way beyond seeing-eye dogs and mobility assistants in the past few decades. For example, specially trained dogs are able to respond to autistic children on the verge of a "meltdown," or warn parents of imminent diabetic emergencies and epileptic seizures. Others provide comfort to children suffering from post-traumatic stress, or help children with sleep disorders get through the night.

Of course, most dogs serve in several ways; each is carefully trained for a specific child and highly attuned to his or her physical and psychological well-being.

In her new book, Melissa Fay Greene focuses on 4 Paws for Ability and its forward-thinking founder, Karen Shirk. Shirk's agency is one of the first to place service dogs with children, and one of the first to appreciate the possibilities for service dogs to people with cognitive, emotional and behavioral disorders. Many chapters are devoted to before-and-after portraits of children who receive the 4 Paws dogs.

One withdrawn child, suffering from post-traumatic stress and attachment disorder, is panicked by the introduction of a dog to the family but the happy-go-lucky retriever gradually wins her heart. For a boy deemed too fragile for a dog by most providers, his dog helps him make friends among children who were previously intimidated by his wheelchair and breathing machine.

For a boy on the autism spectrum with a tendency to wander off, his dog always tracks him down and becomes a kind of small-town mascot. Again and again, Greene shows how service dogs improve the lives of children and their families. The stories always pack a sentimental punch, but perhaps the most heart-tugging chapter is the one about Eddie, whose life gains meaning when he starts training papillons for future service while serving a life sentence at a nearby prison.

Greene uses the stories to frame questions about the emotional intelligence of dogs. Can they experience empathy? Do they love their owners? Do they grieve? She takes sidesteps into scientific literature, but her own position is clear. Absolutely, dogs love, and absolutely they grieve. They not only experience empathy, they exemplify it.

As an unabashed champion of her furry protagonists, Greene tends toward magical thinking over evidence and emotional involvement over journalistic detachment. She even ultimately seems to endorse the "Lassie myth," the idea that a dog can fix everything, even while admitting that trainers go to lengths to dispel it. The families she writes about must be similarly inclined.

Kurtis Scaletta is a writer and book critic in Minneapolis.