Jim Goodwin scored a screamer as St Mirren eased into the last eight of the League Cup at the expense of St Johnstone in Perth.
Jamie Adams headed in an own goal on 38 minutes after good work from the excellent Steven Thompson.
And Goodwin hammered in a terrific, angled strike from 25 yards right on the half time whistle.
St Johnstone offered little in the second half, with Craig Samson saving comfortably from Cillian Sheridan.
The home side, who saw their five-game unbeaten run come to an end, were distinctly below par given their impressive 3-0 victory at Motherwell at the weekend.
St Mirren, 2-0 losers at Hearts on Saturday, went on to dominate the first-half, with teenage midfielder Kenny McLean stinging the palms of goalkeeper Peter Enckelman with a 20-yard drive.
Home defenders Steven Anderson and Dave Mackay were then involved in a tangle, with Gary Teale almost profiting as he chipped wide.
The hosts finally threatened on 21 minutes when Francisco Sandaza wriggled free on goal after a Sean Higgins pass, but his shot was blocked and Liam Craig's follow-up was weak.
The breakthrough came when Thompson's header back across goal was set to be headed in by McLean, only for Adams to do the job for him from close range.
Then, on the stroke of half-time, Goodwin doubled the lead with a stunning finish, with a fizzer that flew past Enckelman.
St Johnstone defender Dave Mackay had an effort held by Samson before Sherdian headed straight at the visiting keeper.
St Johnstone continued to dominate second-half possession, but created little in the way of clear-cut chances.
On the break, Teale saw an effort saved by Enckelman at his near post before Sheridan looked to have pulled one back on 81 minutes only for Samson to scramble his header away from danger following a Craig delivery.
St Mirren manager Danny Lennon: "I'm absolutely delighted. It's a very, very difficult venue to come to and a very, very difficult team to play against.
"You know you are in a game of football here.
"You have to go and earn the right to play and in the first half I certainly felt we did that.
"The first-half performance was very, very good at any level. We had a dominance of possession.
"We were creative but we also had guys with big hearts out there who were hungry for that victory."
St Johnstone manager Derek McInnes: "The damage was done in the first half and I felt the better team won.
"I thought we never really treated it like a cup tie until it was too late.
"We've got a lot of injuries at the moment, we just looked off it, compared to where we have been."