4:24 p.m.

Grinding up the mountain Courtesy of Team Angels

Lisa hits the Powerline descent, a skinny trail down a steep hill crossed by slick roots, large rocks and poles from the powerlines that run overhead. A group of guys have positioned themselves right next to the first big drop off, and they scream, chant and clap as riders pass, urging the racers to push their limits. In the 20 minutes before Lisa arrives at least two guys eat some serious turf, one of whom must be escorted out by a medical team, his head wrapped in gauze.

This is Lisa's first 24-hour race and she admits she's been having dreams about being the weak link. "When it's just you," she told me earlier, "It's not a big deal, but when you're on a team, you let everyone else down if you screw up, and these girls really want to win." To make matters worse, the rotation has worked out so that Lisa is up against the second place team's best rider.

4:55 p.m.
Robin waits for Lisa, mostly still staring off in the distance. Soon she sees one of the women from Las Mariposas. "You freaking out yet?" the woman asks her.

"Yeah, are you?" Robin responds.

"Of course." They both go back to staring past the trees.

5:04 p.m.
Lisa's in after a 1:42 lap. The lead is down to 9 minutes but the relief on her face is visible. "I was so afraid to get passed," she says.

"The roots are super slick...I did a lot of crashing out there. It was hard."

5:29 p.m.
Back at the condo, Sarah pumps her fist as we pull into the parking lot. Inside, Amy has showered and hit the jacuzzi and is getting ready for a massage. The washer and dryer run, as they will almost all weekend long, cleaning dirty uniforms between laps. There's a big marker board on the wall listing all the lap times and the lead, which Amy continues to analyze aloud as she sips yogurt and strawberry smoothies. Lisa emerges newly showered and begins to calculate when her next turn will be. This quite possibly is the difference between women and men.

Sequestered in their condo, the Angels are tea party civilized and far removed from the throbbing underbelly of the event - the wet riding gear, the cramped tents, the true whackos, like The Four Elvi, four guys who are riding the entire race in full Elvis regalia. Or Team Hugh Jass, two maniacs who share a single-speed bike and ride in cut-offs and an old motorcycle helmet. "I've done the camping thing," says Robin. "Never again."

7:45 p.m.
The Airport climb is the highest point on the course and it comes after a steady two-mile ascent up a fire road at about a 4% grade. After that you have to navigate a steep singletrack switchback deeply rutted and covered with loose rocks and gravel. I watch about 200 riders go by and only four make it up without having to get off and push. Most of them are sucking wind so hard they can't speak. One guy pulls out a disposable camera and asks me to take his picture. "My teammates would kill me if they knew I was doing this."

Sarah reaches the Airport climb and makes it halfway up before she has to hop off and push. "Feeling good," she says as she goes by. The feeling won't last though. By the time she makes it back in, she has severe cramping in her thighs and is feeling nauseous. She has, however, completed her lap in 1:33 and extended the lead to 30 minutes.

9:15 p.m.
At the condo, Robin thinks about her daughters, who are following the race at home on the Internet. In the weeks leading up to the race, Robin would fret about her performance, and the older one would tell her, "Don't worry Mommy, you're the fastest mountain biker woman in the world."

10:06 p.m.
The night rides are always a bit slower as the racers grapple with the course aided only by two semi-reliable, battery-powered lights - one on their helmet and one on the handlebar. Amy turns in a 1:48 lap, and once again seems to have only slightly less energy than when she started. The lead has dropped to 24 minutes as Lisa heads out for her first ever night lap.

10:38 p.m.
Robin paces in the pit area while Scott, Amy's husband and the team mechanic, explains that she broke two spokes on her last run and that her wheel, which is old, could go on her if she's not careful. A mechanical breakdown, even a flat tire, could easily evaporate a 24-minute lead. What's more he says, "Your shift cable is sticking. Going to the higher gears is fine, but downshifting could be a problem."

"That's fine," Robin replies, "I'm probably going to run the whole thing anyway except the downhills."

11:16 p.m.
Spotters wait for Lisa atop one of the long climbs. Below, little white dots quiver through the valley, then rise up out of the pitch darkness. The temperature has dropped into the 50s and there's a bit of wind. The sound system plays a country and western version of AC/DC's "You Shook Me All Night Long," adding to the surreal effect. When Lisa emerges from the night she's 20 minutes behind the pace of her last lap.

12:00 a.m.
There's a New Year's-like countdown to midnight and a cheer goes up from the few stalwarts still lingering around the main tent. In the Angels' pit area Scott and the boys have taken to alternating slugs of coffee and beer to help stay warm and awake. Four minutes later Lisa rolls in, completing her lap in 2:00 flat. "The roots are super slick," she says, looking a little bewildered. "I did a lot of crashing out there. It was hard. It was probably the hardest thing I've ever done." Half way through the race, the Angels' lead is down to 15 minutes.

3:56 a.m.
After laps of 2:00 by Robin and 1:49 by Sarah, the Angles' lead has jumped to 37 minutes. Amy takes off on what will be the last of the night laps. If she can hold the lead to daybreak, the odds swing more heavily in the team's favor.

5:31 a.m.
Snapshot of the condo: plates with half eaten sandwiches, a crusting-over tin of lasagna, open Gatorade bottles, cups, cans, shoes, clothes and gear everywhere. A giant bottle of Motrin sits open on the counter. Somewhere in the distance someone coughs, then it falls silent again.

5:50 a.m.
Sunrise over the eastern rim of the mountains. Amy's in on a 1:53 lap and the lead holds at 37 minutes. It's substantial, but not insurmountable. One error, one wipeout, one teammate sick and puking on the side of the trail could change everything.

7:40 a.m.
In the condo, Robin leads a strategy session. Lisa had been cramping before she went out, so how well she'll be able to hold off the other team's rider, who's been consistently faster, is a question. Also, Sarah, the Angels' fastest rider, is feeling weak and nauseous, and Robin wonders if they'll have to skip her and send Amy out on short rest. At the same time, there exists the very real possibility that the other team will skip its slowest rider and double up its faster rider over the last few laps in order to close the gap. Robin herself feels tired, saying that like Lisa, she only managed to doze briefly between calf cramps.

7:45 a.m.
When Lisa hits the finish, covered in mud, shorts ripped diagonally across the left thigh, the gap is down to 24 minutes.

9:38 a.m.
Robin picks up four minutes before handing off to a shaky Sarah, and that is when Sarah loses it trailside. Right there, not 30 yards from the start of a grueling 12-mile lap she's down. For a moment, everyone stands frozen, unsure what to do. Then, between heaves, Sarah looks up, "Once I get it out I'll be all right," she says. "I'm not afraid. I'll be okay." She pukes one more time, then gets on her bicycle and goes.

10:45 a.m.
Worried if Sarah can gut it out, the Angels send spotters out to track her progress. At the first check point, she's doing well, but falling off her pace. Since then, almost 45 minutes ago, she hasn't been seen.

11:21 a.m.
True to her word, Sarah makes it back. Unlike her other laps, in which she increased the lead, this time she has given some of it back. Although 12:00 will signal 24-hours, being in the lead at that point isn't enough. The Angels must finish a complete lap with the lead. It's possible to be leading after 24 hours and still lose. In fact the pressure is even higher now because there's no chance to make for lost time. The slightest problem, an injury, a blown tire, a loose rock that leads to a bad spill could end it. Amy heads out unaware of how big a lead she has, but knowing it's less than 24 minutes.

— Courtesy of Team Angels