That precocious urge to defend the natural world drew upon his own experiences on his family’s estate at Hickory Hill, in unspoiled Virginia horse country, and at their Hyannis Port compound on the pristine shoreline of Cape Cod.

But after a moment, Kennedy realizes he couldn’t have been quite 10 yet when his father trundled him around the hallways of official Washington, asking his uncle’s appointees about birds and pesticides. It is a minor but poignant correction. For by the time young Bobby turned 10 in 1964, JFK had been killed in

Dallas, and things had started to change irrevocably for the Kennedy family and the country. Four years later, when he was 14, his father, Robert Sr., was shot dead in a Los Angeles hotel while celebrating a crucial victory in California’s Democratic presidential primary.

In the aftermath of those traumatic events, Kennedy lived 15 years of a prolonged and painful “ adolescence” that included periods of dissipation and aimlessness. During those years, however, he managed to graduate from Harvard and earn a law degree from the University of Virginia—which eventually allowed him to find purpose, redemption and joy in the same mission that had attracted him as a child.

THE WATERKEEPER

Today, Kennedy is 53, with a house in Westchester County, a large family and a demanding career as an environmental activist, nonprofit executive, law professor and best-selling author. His critics call him an environmental fear-mongerer, a radical and worse, but to fellow activists such as Al Gore, Leonardo DiCaprio and Laurie David, producer of the Academy Award-winning documentary An Inconvenient Truth, he’s a hero. Yet the hero somehow still looks boyish, wearing the required suit and tie with the restless, rumpled style of a man much more comfortable in outdoors gear. More important, perhaps, he still maintains the defiant idealism of youth.

Disdaining the caution and calculation that are characteristic of middle age, Kennedy doesn’t shy away from controversy, whether he is indicting mercury pollution for the rising incidence of autism among American children or seeking to prove that the presidential election of 2004 was “stolen” from