We rented a Toyota four-wheel drive in Dar es Salaam from a sharp dressed man who called himself Kennedy, then drove west into the heart of Africa.

It was my third day in Tanzania. I had run each morning in Dar es Salaam, through crowded streets that smelled of wood smoke and raw sewage, past tall Masai warriors dressed all in red and very far from their homes in Kenya, past the train station the Germans built when they controlled Tanzania, and the American embassy blown up by Al Queda long before anyone but the most informed knew that name.

It was a world of pavement and exhaust. There were pedestrians everywhere, but I was the only runner and drew stares. Yet I savored each step. There would be no running in the wilderness where we were headed.

As we drove west, the city was soon replaced by a low-lying coastal jungle. The pink backs of immersed hippos dotted the surface of one river. An hour later, after we'd crested a long hill, we gazed out across a sun-baked savanna, its tall grasses studded here and there by the iconic silhouette of Acacia trees.

I was traveling with my friends Dave and Bill, who had come with me in search of a great adventure. That night we toured the Mikumi Game Park just before dusk, driving slowly past a pack of hyenas before parking next to a male lion sleeping in the shade so that Bill could take a picture.

The savanna, as far as the eye could see, was a perfect place to run. The roads and trails were hard-packed dirt, and easy on the body. The landscape was neither hilly nor flat, but a rolling expense that was made even more inviting by the biggest bluest sky I have ever seen.

But the instant Bill rolled down the window to take his picture, the reason I would never run on the African savanna became quite obvious. That sleeping lion flicked one eye open and tensed his haunches, waiting for Bill to do something foolish like set foot outside of the car. To run in or around the Mikumi would have made me prey.

We spent the night at the Genesis Guest Lodge. The Genesis was a collection of small wood-floored rooms arranged around a courtyard and al fresco restaurant. Dinner was carrot soup and splendid chicken curry, all served on a checkered tablecloth. The waiter wore a white shirt and bow tie and looked like Louis Armstrong. "Do you think there's something weird about Chowa?" Dave asked as we ordered a second round of Safari Lager. Chowa was our driver. We had offered to rent him a room but he refused, then went somewhere with the car after dropping us off. We were having doubts he would return.

Dave hit the table softly with a flat hand. "He speeds up every time he sees a police car, understands English when it suits him, and now he disappears with the car. Something about that guy just isn't right."

I left to use the bathroom. It was in the back of the restaurant, down a long dimly lit corridor. The walls were glass and, as I began walking down the narrow hallway, they seemed to actually be moving. The sensation was so real that a chill ran down my spine. My first urge was to bolt back to the restaurant, but that would have been silly. I took a deep breath and forced myself to stifle that impulse. I bent closer to the glass to study the phenomenon.

Staring back at me, nose to nose, just a fraction of an inch away, was a black mamba, one of the world's most deadly and aggressive snakes. I gasped and leapt back, almost falling back against the glass wall on the other side of the hallway. Cautiously, ever so cautiously, I leaned forward again.

There wasn't just one mamba. On the other side of that thin pane of glass was a writhing, squirming collection of at least a dozen black mambas. They were skinny and long like a whip, and they kept trying to slither their bodies up the face of the glass to seek a way out.

I stepped back again, then took a closer at the other panels of glass along the hallway. They were all filled with snakes. The section just behind me – the section I had nearly crashed back against — was a collection of puff adders, fat slovenly snakes as thick around as softballs. They looked far less aggressive than the mambas, but I knew they were just as deadly. The craziest thing about these encounters was the glass separating me from the snakes was not hermetically sealed, or even thick aquarium glass. It was cracked, brittle and quite obviously pre-owned, as if it had once been an inconsequential windowpane on someone's home.

And yet I still needed to use the restroom.

I stepped cautiously down the hallway. With every step I experienced an amazing herpetology collection slithering up the thin glass: mambas, adders, pythons, Egyptian cobras and a particularly nasty King Cobra that flared his hood and lunged to attack me, hitting the glass instead. I wondered how much force it would take to break the thin pane, and how much time I would have to run away if a snake did so. Just as I left the creepy confines of the hallway, thinking the natural wonders behind me, I almost stumbled into the crocodile bathing in a small pool of water next to the men's room. Welcome to Africa, I thought, where you never know what's going to happen next.

That night I slept under mosquito netting in room 106. We were up before the sun, awakened by the Muslim call to prayer and a rooster that began crowing at three a.m. Breakfast, after a bracing shower, was a Spanish omelet with garlic chili sauce and a coke. It was still very dark as we stood in the gravel car park hoping for Chowa's return, the air smelled of dust and dry grass — just the way I always imagined Africa would smell.

A full moon the burnt yellow color of South Dakota sunflowers was setting over mountains to the south. It was cold, and my teeth chattered lightly.

This was a moment made for running, the perfect time of day to pull on a pair of shoes and run down that ribbon of highway in the cool morning air. But that highway was lined on both sides by the tall grass. And that tall grass could conceal almost anything. Perhaps tomorrow, I told myself. I could run tomorrow, when we got to Kigoma.

"You think he's coming?" Dave said, looking down the road. As if on cue a set of headlights came around the bend, then drove into the car park. Chowa stepped out of the sports utility vehicle without speaking. He was built like a fullback, wore polyester slacks and a short-sleeved madras button-down, and smelled as if he avoided bathing.

I unfolded the map of Tanzania on the hood and, by the light of my headlamp, showed him where we needed to go. Our route for the day would take us to Tabora, a vital crossroads on Henry Morton Stanley's 1871 search for Dr. David Livingstone. There was a house on the edge of town where he had spent several months during the journey, and where one of his traveling companions was buried.

Chowa shook his head. "We will go another way."


"But we really need to follow this specific route, Chowa," I said, trying to be firm but polite. "This is why I've come to Africa."

Chowa seemed a little scared. His demeanor was surprisingly meek for such a large man. "There are bad men on that road."

"OK," I said, looking closely at the map. That made sense to me. "Which way?"

"Here," Chowa showed me, tracing a finger along the map's red highway.” To Mbeya, then Tunduma, then Kigoma."

Though a path David Livingstone once trekked, it was almost the exact opposite of where I needed to go to research my new book. The route would take us southwest, toward the Zambian border, before a sharp right turn would take us off the highway and onto a dirt road which we would follow for several hundred miles to Lake Tanganyika, bypassing Tabora altogether. At the very minimum, we would be on the road until midnight. "Let's get going," I sighed, resigned to the detour.

The road climbed as we left the Genesis and headed into the Kirk Mountains. The moon lit the dark highway, and between the silhouettes of trees and the thatched roofs of villages, a silver stream trickled in a ravine far below.

An hour passed. We didn't see a single car. Suddenly, we came upon an overturned cattle truck, partially blocking the road. Chowa threaded through the wreckage as the Indian owner retrieved his cattle from roadside gullies. A mile later the fastest of the bulls and cows were having a Tanzanian running of the bulls, right down the middle of the highway. They moved to one side as we came upon them. We drove next to them for a moment, our pace matching theirs. I sat against the left side window and looked into the eyes of a bull. He was determined and showed no sign of fear, perhaps unaware that his flight to freedom would soon make him lion food.