Esmael Goncalves was St Mirren's goal-hero as his double knocked St Johnstone out of the Scottish Cup.
The Portuguese striker looked sharp early on before home keeper Craig Samson saved brilliantly from Steven MacLean and Rowan Vine.
Goncalves' headed his first past Alan Mannus from Gary Teale's cross.
And he got his fourth goal in three games after collecting Steven Thompson's flick to net a low shot under pressure from two defenders.
These two sides last Scottish Cup meeting came in the 2007-08 season when the Perth Saints comprehensively won replay at St Mirren's old Love Street ground.
St Mirren's Goncalves got pulses racing in Paisley after 10 minutes with a mazy run through the visitors defence which David McCracken dealt with fairly.
Good early signs, though, from the Portuguese striker who has made a great start to life in Scottish football.
And it was he who escaped the attentions of St Johnstone's Frazer Wright down the wing in the 18th minute to put in a tempting cross for Thompson, who could only turn it wide.
Perhaps frustrated by St Mirren's bright start to this cup-tie, St Johnstone's Paddy Cregg unleashed a two-footed tackle on Thompson which brought the yellow card out of referee Craig Thomson's pocket.
Shortly after, Cregg followed that up with a 20-yard shot which was dragged well wide - St Johnstone's first clear chance of the match.
But they carved a much better opportunity just after the half-hour mark.
Home keeper Samson showed great reflexes to turn MacLean's effort round the post after the striker got on the end of Vine's cross-come-shot.
The stopper rescued his side again with a superb one-handed save to prevent Vine's header hitting the top corner.
Samson's heroics were definitely not required, however, just before half-time when the unmarked MacLean slashed Gregory Tade's pass over from just inside the box.
After the turnaround, Goncalves rose to splendidly head Teale's cross from the right past a sprawling Mannus for the opening goal.
And on 56 minutes the 21-year-old had another goal.
This time Thompson's flicked header found Goncalves near the penalty spot. He was under pressure from McCracken and Wright but still carved space to roll a low shot past Mannus.
Not happy with two, he nearly had his hat-trick 60 seconds later but his curled effort narrowly missed the far post - the Perth side not knowing how to cope with St Mirren's January signing.
St Johnstone brought on Nigel Hasselbaink as well as recent captures Gwion Edwards and Mehdi Abeid to try and halt their impending Scottish Cup exit.
A 25-yard rising Teale free-kick flashed wide of Mannus' post before Goncalves spurned a further opportunity to make it a hat-trick.
With five minutes left, St Johnstone's Liam Craig again brought out the best in Samson with a bullet header which the big goalie clawed away.
Even in injury time, St Mirren's goalkeeper had to graft hard to maintain a clean-sheet - blocking Hasselbaink's close-range shot.