The road is a little like the one to Oz. If you just follow the C&O Canal towpath, one foot in front of the other, you can't get lost.

Harpers Ferry lies 62 miles ahead. Sixty-two and one-seventh miles, to be exact. Joe Greene knows the route down to its last inch, down to its slightest incline and curve. He's walked it four times -- and each time, he's done it in about 19 hours.

Greene's not the only one who makes this yearly pilgramage. The Sierra Club sponsors a hike to Harpers Ferry every April, and every year about 40 otherwise sane individuals pit leg muscles and feet against the grueling distance.

They do it for the exercise, for the camaraderie and for the sheer challenge of seeing whether or not they can finish.

The Harpers Ferry hopefuls have recently begun training together on weekends. "It's a real team thing," said Greene. "These are the people I'll be with every weekend until the end of April. It's the one time a year I really get a feeling of doing something together with a group of people."

The training consists of weekly hikes, usually along the canal. They increase in distance; by April, the hikes will go for 30 miles at a shot.

"It's an addiction," said Sue McElfresh, who, with Greene, is one of the organizers of the April 26 hike. "You're in absolute pain at the end. But somehow you forget that after you're done, and are ready to go at it again.

"It's like having a baby."

The hikers leave from Thompson's Boat House, near the Watergate, at three in the morning. Volunteers maintain four food stops along the way, and there are cooking facilities, showers and beds awaiting them at a hostel in Harpers Ferry.

They walk all day. "There are highs to the trip," said Greene. "We usually plan the trip around the full moon, so the hiking under the moon is great. Dawn is beautiful. And finishing is great."

But one must take the bad along with the good. "By the end of the hike, I wonder -- I mean, really wonder -- what I'm doing here. I wonder in every aching pore. That's when I need other people for inspiration," Greene said.

According to those who have completed the hike, there are two mainrules to finishing. You have to walk along with someone else to keep your mind off your suffering. And you can't stop too long to rest.

"If you stop for more than a few minutes, it's all over," said McElfresh. "You tighten up and you'll never get up again."

Some very energetic souls run or race walk the distance. "We never see those people," she said. "They don't train with us. We see them at the start of the hike. Then they're so far ahead of us, we never see them again. By the time we get to the hostel, they've already taken their showers and gone to bed."

People of all ages join in. "Sure it's crazy," admitted McElfrish freely. "But what the heck? Shopping at Springfield Mall on the weekend is no way to relax after a week at a stressful job either."

Even with the training, of course, not everyone can walk 62 miles. Those who have difficulty can usually get a ride back to Washington with the food-station volunteers. Then, they have a whole year to think about what went wrong and how to make it the next time around.

"This will by my third try," said Jim Finucane ruefully. "The first time I walked as far as White's Ferry -- 37 miles -- and my ankle gave out. The next time I wore hiking boots for my ankle. My ankle was fine. But then my toenail fell off."