There is an American who grew up in a bus and on a boat with his eccentric family on Florida's Gulf Coast. As a boy, he would lecture his family on natural wonders like snakes and bugs. Then he got a full scholarship to Duke and, during his education, noticed the Haitian workers in the North Carolina fields and nuns standing up for the Haitians' rights when no one else would.

He saw that Haitians everywhere, like the fruit pickers he grew up around, repeatedly get the short, hard end of the proverbial stick, so he went to Haiti in 1983 with vague anthropological notions, a desire to help and some mighty brain power. He found a country with the worst health statistics in the West; 25 percent of Haitians die before reaching the age of 40. The per capita income is just over a dollar a day.

There Paul Farmer discovered his mission. Seven years later, he graduated from Harvard in 1990 with two degrees, one in medicine and one in medical anthropology. He may have pulled the strangest commute of any Harvard student because he lived, studied and trained in the clinic he helped to establish in Cange, Haiti; he appeared in Boston long enough to buy books and take tests. His grades were outstanding.

He was 31 and hell-bent on changing the accepted injustices and ideas about poverty and health care. Since then, it's fair to say that Farmer and the equally talented, devoted people of his organization, Partners in Health, have changed the world.

Tracy Kidder, winner of a Pulitzer Prize for The Soul of a New Machine and a contributor to The New Yorker, is no slouch himself, and this wonderful book brims with the energy of those infrequent perfect collisions of author and subject. A lucid, graceful writer, Kidder captures Farmer's humor, devotion, passion and humility so that a reader has the distinct impression of having been in Haiti, Cuba and Moscow with Farmer.

The book's only disappointment, entirely unavoidable, is that it ends.

But the story is ongoing: Farmer is still rushing around out there - cracking jokes, not sleeping, missing his wife and daughter, flying from Haiti to Peru to Russia and not only changing how the World Health Organization deals with disease but improving the health of a million peasant farmers and families in Haiti's Central Plateau.

Begun without a real master plan in 1983, the Cange clinic was the seed that sprouted PIH. Farmer met Boston construction mogul and philanthropist Tom White through a charity there, and White bankrolled the clinic for years. White's support and quiet humility are pillars of PIH.

A good example of Farmer's spirit as a complement to White's support is the story of Cange's first microscope: Farmer stole it from Harvard. He later said: "Redistributive justice. We were just helping them not go to hell."

Farmer's humor is a constant buoy throughout the book, and one can only imagine its life-saving qualities for him. When he first brings Kidder to Haiti, he guides him through a Latin-laced tour of the plants and trees growing around his hut, acknowledging that it is "hortitorture."

In his clinic office, he tries to lay low and get some work done because he is always besieged by chatty Haitians the moment he walks out: "Farmer sits down at his desk. 'Now the objective is?' He looks at me. I shrug. He says, 'To stay put. Because people are lurking outside. Lurkaceous behavior.' "

His trips through the Haitian clinic are alternately tender and heart-breaking. At one point, he performs an emergency spinal tap on a young girl and she cries out two things in this order - she is hungry and it hurts.

Jim Yong Kim and Ophelia Dahl helped to start PIH with Farmer, and Kim would later branch out and open a clinic in Carabayllo, a slum on the outskirts of Lima, Peru. There Kim and Farmer, who visited frequently, would make an alarming discovery: Peru's highly praised tuberculosis program, which followed WHO guidelines, was also creating a strain of TB resistant to all known treatments.

If a patient began TB treatment and then stopped for myriad reasons that involve poverty and then tried to begin the treatment again, the TB would likely have a resistance to the drugs. Continue the pattern a few more times and there is a TB strain immune to all known treatments and it could easily spiral into an international epidemic.

Kim and Farmer created a plan that flew in the face of the accepted ideas about treatment costs and poverty to combat TB, which kills two million people a year. This led to a $45 million grant from the Gates Foundation and Kim then led a movement through the WHO to drop the prices and increase the availability of TB drugs. It worked. In an e-mail to PIH, Kim wrote, "The world changed yesterday."

Farmer inevitably is involved in increasingly international projects but his true passion is Haiti and the people there. He will hike seven miles into the remote countryside looking for tardy or missing patients.

Haiti continues to fester with the reins in the hands of an ineffective government that has only inspired the U.S. to cut loans and funding to the country. Kidder writes:

"Haiti was still bleeding away, like its topsoil. Aid to the government remained choked off. There was no end in sight to the country's degradation.

"The whole situation was 'rotten,' Farmer wrote. He added, 'But there are some spots of hope.' "

Kidder has written a powerful book about one of the brightest spots.

Tyler D. Johnson is a multimedia producer for the Rocky Mountain News.