Michael O’Halloran scored twice as St Johnstone beat a Motherwell side that had three men sent off.
Steven MacLean’s flicked shot and O’Halloran’s first put Saints in charge but Well’s Andrew Rose headed one back.
Goalkeeper Trevor Carson was dismissed for handling outside his area and O’Halloran fired his second.
O’Halloran also had a penalty saved after Carl McHugh and Charles Dunne had been sent off and Murray Davidson swept in Saints’ fourth late on.
Though Saints exited the League Cup in midweek and Well progressed to the last eight, the two sides have had contrasting starts to their Premiership campaign with St Johnstone now on two wins out of two and Motherwell having lost their opening two league games.
And Tommy Wright’s side were quick out of the blocks. MacLean was the sharpest player in the box, the veteran striker reacting well to lift the ball past Carson from close range after Stefan Scougall’s shot had been partially blocked.
The hosts were soon two up. O’Halloran gathered on the left wing before drifting in dangerously to the Motherwell box and guiding a curled right-foot shot just inside the far post. It was a goal that underlined just what a big player he could be for St Johnstone this season.
The Motherwell defence looked shaky. From a corner Davidson got a head to the ball at the near post, but his effort flew over.
The initial St Johnstone pressure relented slightly and Motherwell got a free-kick 35 yards from goal. The ball was lofted in to the box and Cedric Kipre flicked it on to the back post, where Rose was waiting to nod home from two yards out.
Gael Bigirimana fired just wide and Rose was denied a headed second by Alan Mannus’ save early in the second period.
Given their uncertain start, Motherwell started to dominate the play and threw on striker Louis Moult.
But then the roof fell in on the visitors. Under pressure to gather a long through ball, Carson picked it up. Referee Craig Thomson ruled that the keeper had handled the ball outside his area and immediately brandished a red card.
It was a hammer blow for the away side, who immediately sacrificed Bigirimana as back-up keeper Russell Griffiths took to the pitch.
There was nothing Griffiths could do as O’Halloran conjured up another moment of class. A great run from the on-loan Rangers winger ended with a drilled low shot into the centre of the net.
Then the roof caved in on Motherwell as McHugh – already on a booking – was shown a second yellow card for a late lunge on Brian Easton.
Incredibly, Motherwell were then reduced to eight men after Dunne tripped Graham Cummins in the box. O’Halloran stepped up to take the resulting penalty but he was denied a hat-trick by Griffiths’ save.
But there would be a further St Johnstone goal, Davidson finishing confidently at the edge of the box following Richard Foster’s cut-back.