Halmstad took the lead immediately after four minutes when Marcus Antonsson, who is on loan from Malmö FF, skillfully nodded in a post from the right.
IFK Norrköping did not really get the game to work and coach Rikard Norling looked annoyed at the bench.
Right at the beginning of the second, Norrköping had a ball in goal, but this time the new acquisition Samuel Adegbenro was offside.
HBK wanted a penalty
Shortly afterwards, HBK wanted a penalty when defender Joseph Baffo fell in the penalty area, but referee Bojan Pandzic chose to release.
IFK Norrköping took over the game more and in the end Adegbenro got a dividend.
He got a back pass and pulled on a shot from just outside the penalty area.
The goal was the Nigerian's first in the Allsvenskan.
The talent decided
With ten minutes left of regular playing time came the liberating 2-1 goal for "Beijing".
But it became an emotional roller coaster.
The Icelandic great talent Isak Bergmann Johannesson poked the ball from close range, but it was first wrongly ruled out for offside.
Namely, it was Halmstad's left back Andreas Bengtsson who tried to nod the ball to his own goalkeeper when the Icelander came forward and scored.
The Norrköping players were furious when Pandzic blew for offside, but all the happier when the referees changed shortly afterwards after discussing among themselves.
The victory was IFK Norrköping's first in this year's Allsvenskan. The newcomer stands at three points.