“Perhaps the power of Matthiessen’s writing in part derives from his ability to tap into his dark side, his Jungian shadow,” a biographer, William Dowie, wrote. “If so, it would explain at least one similarity between him and the writers to whom he is sometimes compared in his major fiction: Melville, Conrad and Dostoyevsky.”

Indeed, Mr. Matthiessen’s Watson carries an echo of Conrad’s Mr. Kurtz, the corrupted jungle lord in “Heart of Darkness.”

“Even a quarter-mile away, out in the channel, the figure at the helm looked too familiar, the strong bulk of him, and the broad hat,” Mr. Matthiessen writes in the voice of a character named Mamie Smallwood. “When he saw the crowd, he tipped that hat and bowed a little, and the sun fired that dark red hair — color of dead blood, Grandma Ida used to say, only she never thunk that up till some years later, when the ones who never knew him called him Bloody Watson.”

She goes on: “But it was that little bow he made that told us straight off who it was, and my heart jumped like a mullet, and it weren’t the only one. A hush and stillness fell on Chokoloskee, like our poor little community had caught its breath, like we was waiting for a storm to break from high dark thunderheads over the Glades in summer, just before the first cold wind and rain.”

New York to the C.I.A.

Peter Matthiessen was born on May 22, 1927, in Manhattan, a descendant of Scandinavian whale hunters and the second of three children of Erard A. Matthiessen, an architect and conservationist, and the former Elizabeth Carey. He grew up with his brother and sister on Fifth Avenue, overlooking Central Park (in the same building as Mr. Plimpton), and in country homes on Fishers Island, N.Y., and in Connecticut.