Sydney Thunder are through to their second WBBL final after Brisbane Heat lost 6-12 late and what appeared to be a certain spot in Saturday's decider.
Chasing 144 for victory, two-time defending champions Brisbane were cruising at 4-119 before they fell apart in a bizarre climax to the semi-final on Thursday night.
Teenager Hannah Darlington was the hero for Thunder with 3-19, including two wickets in as many balls in the 18th over.
Laura Kimmince had earlier looked like she'd set up the win for the Heat with 37 from just 17 balls but she threw her wicket away at a crucial point.
After both Georgia Vole and Amelia Kerr were run out in the same over with the score on 119, Kimmince appeared as if she'd get Brisbane home with her hard hitting.
Batting fearlessly throughout the tournament with a strike-rate above 200, Kimmince whacked four sixes down the ground.
She had been lucky to survive her first ball from Sam Bates, which bounced off her body and into the stumps only for the bails to stay on.
But the match swung again when Kimmince tried to reverse slog Bates with the Heat needing 15 runs from 19 balls and was bowled off her pads.
Darlington claimed two wickets the next over but missed out on a hat-trick.
Unheralded South African Nadine de Klerk hit a run-a-ball 27 for Brisbane, before she was run out taking on the arm of Tammy Beaumont.
Captain Rachael Haynes had earlier been the calm head for the Thunder, hitting an unbeaten 48 from 44 balls.
The left-hander was measured throughout, using her feet well to the spinners, before helping her side take what proved a crucial 15 runs from Delissa Kimmince's final over.
The win puts the Thunder in to their first final since their victory in the tournament's inaugural season, in 2015-16.
