About four years ago, journalist Mark Honigsbaum traveled to Ecuador to work on a book about malaria. But not long after landing in South America, Mr. Honigsbaum contracted an infectious disease that, unlike malaria, has no proven cure. He caught a bad case of gold fever and spent the next two years of his life stalking a lost Inca treasure.

According to legend, the stash of riches remains hidden in a secret cave somewhere in the mountains of Ecuador. Countless adventurers have set out to claim the treasure in the past, only to die trying. For his part, Mr. Honigsbaum lived to tell the tale, and in his new book (Farrar, Straus & Giroux, 368 pages, $25), he retraces the rich history behind the hoard that touched off his own bout of hot-headed treasure-hunting.

In the summer of 2000, Mr. Honigsbaum traveled from London to the small Ecuadorian city of Banos, hoping to learn more about Richard Spruce, a 19th-century British botanist who once had harvested a nearby source for malaria medication. Upon his arrival, Mr. Honigsbaum found Banos buzzing about Valverde’s gold. Only a few months earlier, the Ecuadorian Air Force had dropped paratroopers into a mountain crater to the northeast of Banos in search of the treasure. The mission had failed, and the gold was still out there.

Mr. Honigsbaum at first ignored the chatter, but during the course of his research he unearthed a past plot to uncover the gold, involving Mr. Spruce and two British sailors. Intrigued, Mr. Honigsbaum kept digging.

The story of Valverde’s gold dates back to the 1532 when the Spanish conquistador Francisco Pizarro captured the Incan king Atahualpa and subsequently demanded a whopping ransom from his people. Before the Incas could turn over the riches, however, Pizzaro executed their leader. Facing the imminent collapse of their empire, the Incas supposedly hid the ransom deep in an inhospitable mountain range called the Llanganatis.

“Legend had it the hoard was immense,” writes Mr. Honigsbaum, “seventy thousand llama-loads of gold and silver weighing some five thousand tons.” That’s a lot of llama-loads. In today’s terms, Valverde’s gold would probably be worth more than all the jewels in Lil’ Kim’s closet.

The treasure takes its name from Valverde, a Spanish gentleman who, about 50 years after Pizarro’s treachery, married an Indian princess, thereby acquiring the best set of in-laws in either history or legend. His new father-in-law divulged to Valverde the whereabouts of the treasure, and for years he treated the cave as his own personal ATM. On his deathbed, Valverde drew up a guide to the riches.

Mr. Honigsbaum was sitting in the library at the Kew Royal Botanic Gardens and flipping through one of Mr. Spruce’s journals when he discovered a copy of this guide. Pretty soon, Mr. Honigsbaum was crisscrossing the planet from Quito, Ecuador, to Seville, Spain, to Cinnaminson, N.J. (where he visits a reclusive codger who is rumored to possess a secondary set of maps to the treasure), piecing together clues to the gold. Along the way, Mr. Honigsbaum ferreted out a eccentric cast of modern-day treasure hunters – a Canadian huckster who sells treasure maps on the Internet; a German arms dealer who has spent more than $100,000 searching for the gold; a secretive Franciscan priest who dodged Mr. Honigsbaum as though he were El Chupacabra.

Unfortunately for all of them, Valverde penned his directions to the treasure in the age before MapQuest. The instructions are famously confusing. The distances are imprecise. The landmarks are oblique (“a left at the Reclining Woman”?) Furthermore, the Llanganatis are treacherous terrain, touched by periodic earthquakes and constant rainfall. “Sandwiched between the Andes and the Amazon, the Llanganatis are a mysterious and unforgiving place,” writes Mr. Honigsbaum. “There is no good time to go.”

Similarly, there is no good time to interview a treasure hunter. They are a universally suspicious lot, loath to share any information lest someone beat them to the gold. As a result, interactions between Mr. Honigsbaum and his subjects grow increasingly absurd as the book progresses. Every conversation becomes a dance of deceit and competition. At one point, what starts off as an interview ends up as a drunken push-up contest.

Mr. Honigsbaum has shaped this convoluted story into a captivating book, however. It is both a suspenseful mystery and an entertaining taxonomy of a certain type, the treasure hunter. His writing is crisp and witty, and he has a winsome knack for uncovering shiny nuggets of insight from dull-looking surroundings. (He discovers, for instance, why librarians dislike treasure-hunters: “It doesn’t matter how many times they promise to use a pencil and respect the regulations governing the handling of precious documents. If they stumble across a treasure map or some other clue to the location of a lost hoard, they are apt to tear the pages straight from the book.”)

Mr. Honigsbaum’s own enthusiasm for the treasure is contagious, and it’s nearly impossible to read “Valverde’s Gold” without thinking at some point about how nice a cave full of Ecuadorian gold would look in your living room. The author’s pursuit of the treasure culminates in his own lengthy expedition into the Llanganatis, and as he plunges into the jungle, suspense builds: Will Mr. Honigsbaum recover the hidden gold?

And if not, how much is a plane ticket to Ecuador?