NEW YORK -- After three damp days at the U.S. Open it finally cleared -- and then the National Tennis Center was visited by a searing bolt of lightning on Saturday night.
Serena Williams, serving to stay in her semifinal match against Kim Clijsters, departed in one of the most bizarre endings ever in a major match. Down 15-30 in the second set, she missed her first serve and then was called for a foot fault on the second -- even though replays did not show conclusively that her foot touched the baseline.
And then, as CBS broadcaster John McEnroe said, "All hell broke loose" at Arthur Ashe Stadium.
The resulting double fault gave Clijsters match point. But Serena angrily confronted the lineswoman who made the call, dropping the f-word liberally and, getting in her face and waving her racket and later the ball menacingly, saying, "I swear to God I'm [expletive] going to take this [expletive] ball and shove it down your [expletive] throat, you hear that? I swear to God."
It was the most angry anyone could remember seeing her on a tennis court.
After chair umpire Louise Engzell discussed Serena's reaction with the lineswoman, she called Serena for a code violation for unsportsmanlike conduct -- her second after a sanction for racket abuse at the end of the first set. That meant Clijsters, by rule, was awarded a point -- the last point of the match, as it turned out.
Tournament referee Brian Earley came on the court, and during the discussion that included the lineswoman, Serena was heard to say, "I didn't say I was going to kill you. I didn't say that."
And so, Serena ultimately lost for losing her temper twice, on a technicality, 6-4, 7-5.
She tossed her racket down, walked around the net and spoke briefly with Clijsters, who told her she was sorry. Clijsters will play in Sunday's prime-time final against 19-year-old Dane Caroline Wozniacki, who defeated Yanina Wickmayer 6-3, 6-3.
What will get lost in the wake of the controversy is that Clijsters -- in only the 13th match of her comeback -- seemed destined to win the match anyway. With some distance, it will be clear that the foot fault call was far more questionable than the series of events that followed it. But it probably didn't affect the final outcome.
"The timing was unfortunate," said Clijsters, crystallizing what happened, "but there are rules.
"You don't expect things go so well so soon."
Afterward, the USTA declined to release the name of the lineswoman.
Serena was asked several times what she had said in anger to the lineswoman.
"I didn't threaten," she began. "I don't remember anymore, to be honest. I was in the moment."
Later she added, "I don't think it's necessary [to describe the outburst]. I'm trying to move on. I wasn't called for a foot fault all year until I got to New York.
"If she called a foot fault, she must have seen a foot fault. I'm not going to fault her for doing her job."
Does Serena regret her loss of temper?
"I try not to live my life saying, 'I wish, I wish,'" she said. "I was out there and I fought and I tried to do my best."
Told by a reporter that the lineswoman had apparently said to the chair umpire that she felt threatened, Serena said, "She says she felt threatened? She said this to you?
"I've never been in a fight my whole life, so I don't know why she should have felt threatened."
Clijsters, in her on-court interview, said she didn't initially understand what had happened.
"No," she said. "I was really trying to be focused for the match point. I started to get ready for the return and I saw Serena talking to the linesman, but I was too far away to hear what was going on."
Going into Saturday night's highly anticipated match with Clijsters, Serena had won 23 of 24 matches in Grand Slam singles play, taking the Australian Open and Wimbledon titles, losing only to eventual French Open champion Svetlana Kuznetsova in the quarterfinals at Roland Garros.
But in a revelation of a first set, Serena wasn't slicing and dicing her opponent into so many bite-sized pieces. Clijsters was standing in there, matching Serena's savage strokes from the baseline, often exceeding them. She also displayed some surprising speed. Serena, who is accustomed to dictating policy and moving forward, found herself backpedaling.
The most telling moment -- and it would later completely change the chemistry of the match -- was not a racket stroke aimed at a bouncing ball. After Serena sent a sloppy backhand into the net to give Clijsters the first set, she snapped her racket at the court. It bounced, executed two revolutions, and Serena caught it cleanly, intact. Then, with a furious swipe, she utterly destroyed it.
You could see the anger radiating out of her head, bending the air around her like a mirage in the desert. Usually, Serena can channel her rage into something positive. This time, it was her downfall.
Clijsters took out Venus Williams in the fourth round and became the first woman to ever beat both sisters in the same tournament twice.
She was unseeded here because she stepped away from the game for more than two years to get married and give birth to her daughter, Jada Ellie, in February 2008; she has her first name tattooed inside her left wrist so she can see it before every serve.
It was a titanic semifinal matchup, featuring two former U.S. Open champions and world No. 1s. In terms of ultimate success, however, Serena held a monstrous edge in major titles (11-1) and head-to-head record (7-1).
All of which made this result so surprising.
After she won the 2005 U.S. Open, Clijsters never had a chance to defend her title. A wrist injury took her out of play in 2006 and she took herself out in 2007 and 2008 with retirement.
Now, she's won 13 straight matches at the National Tennis Center.
In the end, Serena correctly summed up the match this way: "I feel I could have played better, Kim played an incredible match."
Greg Garber is a senior writer for ESPN.com.