Magdalena Eriksson's inexplicable stoppage-time own goal sent Manchester City to the Women's FA Cup final at the expense of holders Chelsea.
Under no pressure whatsoever, Eriksson diverted Demi Stokes' hopeful cross past her own goalkeeper to book City a date with West Ham, who beat Reading.
Chelsea had enjoyed the better of the chances, with Fran Kirby and Erin Cuthbert both striking the woodwork.
But Eriksson's uncharacteristic late moment of madness sent City to Wembley.
Nick Cushing's side, who lifted the trophy in 2017, will now hope to add to their Women's League Cup triumph earlier this season.
That final at Bramall Lane was decided on penalties and it looked as though this last-four tie against Chelsea, who they had never previously beaten in this competition, was destined for a similar conclusion.
Nikita Parris squandered City's best opportunity before the break, dragging her effort wide when presented with an open goal, while Kirby was denied by a smart save by Karen Bardsley.
The Blues carried the greater threat after the break, with Kirby heading against the angle of post and bar and Cuthbert's low strike coming back off the foot of the woodwork.
But it was Eriksson's own goal in the first minute of injury time that eventually proved the difference, denying Chelsea a place in what would have been their fifth final.
Their best hope of silverware this season now lies in the Champions League, with the first leg of their semi-final tie against French side Lyon taking place on Sunday, 21 April.
Chelsea boss Emma Hayes told BBC One: "We controlled the game. We were confident throughout. We didn't get out of second gear most of the time.
"To have lost that way, for a player [Eriksson] who has been outstanding this year, I'm so gutted for her. It's a cruel way to lose a game.
"There are a million games she has kept us in this year. I will remind her of how wonderful she's been this year. We've been beaten by a cruel own goal."
Man City and England midfielder Jill Scott said: "It was crazy. It's a cruel way for the game to end.
"We're obviously ecstatic to be going to Wembley. It was an even game.
"I thought we were destined for extra time but I'm so happy we've got the win."