Lundquist excelled with 22 points, eight rebounds and two assists as Södertälje won at home in Täljehallen in front of 437 spectators.
But it was a victory that sat hard inside.
The teams followed each other for a long time, almost point by point, and the visitors from Norrköping led 44-42 before the fourth and final period.
Then Södertälje made a victory move and won by a ten-point margin, 69-59.
"Norrköping was the better team for three periods with an incredibly good defensive team, but then it started to pay off that Södertälje has more players in the rotation. They found better positions at the same time as Norrköping came to a complete stop in the attack, says SVT's expert Nick Rajacic.
Weak shooting of Södertälje
The next game will be played in Södertälje on Monday evening. Then the home team hopes for a better shooting.
What used to be the team's badge of nobility was at times lousy today. By halftime, they had only set one of 13 attempts from the three-point line, an eight percent efficiency.
"The shot wasn't there today so we have savings for the next game, but I'm super happy we won. Klara was fantastic, says Frida Eldebrink to SVT Sport.
"Notice it's the semi-finals"
Lundquist himself:
"Norrköping played great defense today. It was very physical and nothing was easy. It's noticeable that it's the semi-finals now. But we'll have to watch some extra video tomorrow.
Defending champion Norrköping has far from given up.
"We really feel we can challenge this team, but we have to play well and focused for all 40 minutes, not just 30-35 like we did today," says American Alexa Held.