Venus Williams was made to battle to overcome the unseeded Kimiko Date-Krumm in an extraordinary second-round match played under the Centre Court roof.
The five-time Wimbledon champion eventually prevailed 6-7 (6-8) 6-4 8-6 in an epic two hours and 55 minutes.
An upset looked on the cards when Date-Krumm raced to a 5-1 lead before winning the first set on a tie-break.
But Williams bounced back to win the second set with ease and then clinched it in the 14th game of the third set.
The tale which was unfolding under the Centre Court roof looked set to be a scriptwriter's dream as the world number 57, a former top 10 player who had retired in 1996 only to return to the fold after a 12-year absence, outwitted her more-celebrated and younger opponent.
The 31-year-old American admitted the opening set against a player nine years her senior was tough.
"I was very serious about trying to get the win, even down 5-1 in the first set," said Williams, playing in this venerable tournament for a 15th consecutive year.
"It took me a while to adjust in the first set. I thought she played well and I just couldn't get my racquet on it. She doesn't play anywhere near her age."
Centre Court was stunned to silence when the 40-year-old former Wimbledon semi-finalist, the second oldest woman to reach the second round at Wimbledon, broke the Williams serve in the first and third games.
The evergreen Date-Krumm, combining baseline aggression with deftness at the net, was causing her illustrious opponent - albeit one who has only recently returned to court after five months out with injury - all sorts of problems.
Date-Krumm moved to within a game of clinching the first set at break-neck speed, but Williams, dogged and determined, dragged herself back into contention.
The resurgent American won four games on the trot - surviving two set points in the eighth game - as a remarkable opening set went to a topsy-turvy tie-break.
The Centre Court crowd was agog - some were on their feet, applauding Date-Krumm's Herculean effort to win the tie-break after she had previously squandered seven set points in the first set.
"I thought she played unbelievably," said Williams, who hit 12 aces and 45 winners during the course of a compelling match.
"I thought she had some luck on her side, too, with net cords, balls hitting lines. I thought it was a perfect storm for her to try to get a win. Thankfully, I had some answers."
Perhaps unsurprisingly, Date-Krumm was unable to maintain her first-set momentum, with Williams breaking early in the second set to take a 3-1 lead and again in the ninth before comfortably clinching the set.
By the third set, Date-Krumm's fairytale start was in danger of turning into a hazy memory as Williams broke in the second game, but the veteran broke back immediately to put a nerve-jangling third set back on serve.
It was a question of who would crack first, Williams nearly did in the 13th game but survived to win the match.
The players left their stage to a standing ovation, the crowd appreciative of their contribution to a contest which will live long in the memory.
Date-Krum later revealed weightlifting and interval training had improved her stamina, but laughed when asked whether she felt tired.
"Of Course! I felt it in the beginning of the second set, my body was heavy. But after that I came back. Yeah, I was tired. But, you know, I'm still ok. Maybe on Thursday it'll be a problem."