When Marian Lindberg was a little girl she loved to hear her father tell the story of his stepfather, Walter Lindberg, who, when her father was 10, left him and his mother to go to Brazil in search of gold.

He died deep in the jungles of the Amazon, eaten by cannibals. It is a colorful story and it became an early obsession. Walter’s body was never found. In time, Ms. Lindberg began to question the veracity of the story.

Her book, “The End of the Rainy Season: Discovering My Family’s Hidden Past in Brazil” (Soft Skull Press, paperback, $15.95, 320 pp.) tells the tale of her quest for the truth about Walter Lindberg and so much more.

Ms. Lindberg, who lives in Wainscott, is a senior staff writer for the Nature Conservancy, an international environmental organization that has a significant presence on the East End, and, incidentally, Brazil. She has been a newspaper reporter and a lawyer. The skills acquired in both occupations helped her as she unearthed the true story, so far as it can be told, of Walter Lindberg.

There are many facets to the story. It begins with the sinking of the ocean liner Vestris in 1928, as it was bound for Brazil. More than 100 people died. One of the survivors was Otto Ulrich, Walter’s business partner. Lost was the mining equipment that was going to be used to find the gold. Walter did not sail with his partner, ostensibly to spend a few last days with his wife and stepson. In actuality, it was to dally with his mistress. Otto and Walter did eventually meet in Brazil. Then it seemed that all traces of Walter disappeared.

But Ms. Lindberg is dogged in her pursuit. She pores over documents in the National Archives. She finds little tag ends of information that lead her to Brazil, where she is helped by a small group of researchers, to find that Walter has been transformed into Waldomiro Lindberg, a man who owned a retail store in Nova Dantzig, a community of Germans who have settled into what Ms. Lindberg realizes is an earthly paradise. He had also apparently remarried, even though he was still legally married to Ms. Lindberg’s grandmother. References to him end roughly 10 years after he was presumed dead.

Ms. Lindberg interrupts her narrative of the search to detail her own medical difficulties with a cancerous tumor on her pituitary gland. It required that the gland be removed. She undertook the trip to Brazil at great risk, given her own fragile health and the need for constant self-monitoring.

She weaves into her narrative the difficult relations with her parents, particularly her father, who internalized the sense of abandonment that he most certainly felt when his stepfather left. She says, “Dad had only a few years with Walter, and the myth he clung to in place of a father was romantic, strong, and violent. I had to go to Brazil, step into and out of Walter’s shoes, to see the myth of the explorer dead and betrayed in the jungle for what it was: camouflage for a damaged man.”

Ms. Lindberg comes away from her trip to Brazil with a love for the country and its people. She recognizes the magical pull that drew Walter. And, as an environmentalist, she appreciated the magnificence of the great rainforest of Brazil, and its importance to the well-being of our planet.

The people she met in Brazil were unstinting in their help. “All of them,” she says, “came to me like Brazilians to a soccer ball. I hardly had to work for it. They were strangers who knew only that I had traveled a long way seeking answers about my past in a country where I did not speak the language and did not know the way. That was enough for them to want to help me.

“I feel more cared for by this band of strangers than I ever did by my family.”

So why did she undertake this quixotic journey to a foreign land? It defies logic. It almost defies understanding. Yet not quite. The heart has its reasons. She was working out her relationship with her own father.

“[What I] belatedly grasp is that I haven’t been trying to close a wound out of empathy for my father. I have been trying to close my own wound. I am my father insofar as Walter Lindberg is concerned. I am the abandoned child. That’s how I feel.”

This fascinating book is difficult to categorize. It is a family history, a memoir, a story of illness overcome, a celebration of the rewards of research, a travel book, an environmental study, and a mystery. Ultimately, “The End of the Rainy Season” is a self-portrait of a very plucky lady