Devante Cole steered Motherwell into third position in the Ladbrokes Premiership with the only goal at winless St Johnstone.
While Saints remain rooted to the foot of the table, the Fir Park Club trail only Celtic and Rangers after the on-loan Wigan attacker made amends for an earlier miss minutes before the interval.
Home manager Tommy Wright was left to rue the return of last term's penalty curse, with Scott Tanser denied a leveller by Well keeper Mark Gillespie early in the second period.
Midfielder Murray Davidson wasted a gilt-edged chance and Gillespie defied Stevie May at close quarters in a frantic finish which also saw Well's Liam Donnelly sent off.
The first opening was carved out in the 11th minute by the home side, with defender Liam Gordon rising to head Jason Holt's corner wide of the target.
Two minutes later Davidson had time on his side but opted to head Anthony Ralston's cross and his effort was easily held by Well keeper Gillespie.
The visitors should have snatched the lead from their first attack in the 16th minute. Only Cole will know how he managed to scoop James Scott's low driven cross over the bar from point-blank range at the back post.
Motherwell captain Peter Hartley was booked for a 24th-minute foul on Davidson and Gillespie dropped to his right to hold Tanser's low free-kick from the edge of the box.
Perth striker May looked in vain to referee Gavin Duncan when centre-half Declan Gallagher recovered his poise to prevent the recent arrival getting a shot away in the penalty area.
Two minutes from the interval, former Livingston defender Gallagher played an integral role in forging Motherwell's lead. He rose to head down a Liam Polworth corner and Cole was first to react, making no mistake this time by touching a close-range finish into the net.
Saints could have levelled minutes after the restart. Ralston's driven cross caught May off balance and his stumbling touch fell kindly to Gillespie, despite protestations that he had been barged in the back.
Saints did secure a spot-kick in the 54th minute when midfielder Donnelly shoved Davidson but keeper Gillespie guessed correctly to beat out Tanser's effort. He also frustrated May before Donnelly's last-gasp red card for an off-the-ball incident which left Chris Kane on the turf.