"We're screwed," Ralph, our fishing guide, whispered as he pulled up his net and saw that it was empty once again. For the past hour, he'd been scraping it along the bottom of the Putahow River, hoping to scoop up the nut that had dislodged from our propeller, leaving our boat dead in the water.

Ralph, my fishing partner Ken, and I were about 10 miles north of our Nueltin Lake lodge and without a radio. The nearest town was more than 200 miles away, across the watery wilderness of Manitoba, Canada. The lake itself stretched about 100 miles, with a madly serrated coastline and dozens of feeder rivers, such as the Putahow, which we'd steered into a couple of hours earlier. We'd come all this way hoping to hook a trophy fish, but right now we had a more basic goal: get back to the lodge before dark. Ralph put down his net. He looked up at the blue, cloud-studded sky and watched the north wind blowing through the trees. Then he turned to us and said, "We'll sail home."

I had no idea how we'd sail a 16-foot motorboat 10 miles or more, even with a favorable wind. Ralph didn't bother to explain. He used the oar to pole us through the shallows to shore, where he pulled from the boat box an ax, several short pieces of rope, and a brown plastic tarp. "You two better untwine all the rope," he said. "We're going to need all we can get." Then he disappeared into the forest, ax in hand.

Just as we finished de-twining the rope, Ralph returned with a 10-foot spruce tree draped over his shoulder. He hacked off the branches and ended up with a straight mast about five inches in diameter at its base and tapering to two inches at the crown. He roped one edge of the tarp to the pole at two-foot increments. Then he cut a five-foot boom and fastened a third pole to the top of the mast and the end of the boom, completing the triangle of the sail.

That finished, Ralph stared into the boat's bowels. After a prolonged silence, he said, "I have to cut my boat." With the ax, he whittled a hole in the center of the floorboard and lowered the mast into it.

"We can go now," he said.

He told me to take control of the propless engine shaft—now our de facto tiller—and told Ken to man the boom. Four hours later we reached a narrow section of the lake, where, Ralph promised, we'd be spotted by a passing boat, which is exactly what happened. When I look back on that trip, I don't think about the fish we failed to catch that day, or about the huge pike and lake trout we caught later. I remember instead the sound of that brown tarp fluttering in the cool breeze and the gentle sloshing of water against the bow. I remember looking up at an immense sky rimmed with cotton-ball clouds and dotted with arctic terns. I remember the cream-filled cookies that Ralph passed around, the last remnants of our shore lunch. This was my moment—standing at the helm, doing three knots by grace of tarp, twine, and spruce.