A late siege of the Kilmarnock goal couldn’t keep St Johnstone in the Scottish Cup.
After going a goal down early in the game Saints threw everything at Killie in the last half-hour, and saw Jamie MacDonald pull off an astonishing triple save from close range in stoppage time.
But it is the Ayrshire men who will be in the fifth round draw on Monday night.
After just six minutes Chris Millar brought Greg Kiltie down at the edge of the box and Slater gave Alan Mannus no chance with a curled free-kick into the top corner.
It was a real struggle for Saints in the first half, summed up by a David Wotherspoon 25-yarder that soared over the bar midway through it.
Twelve minutes from the break Dave Mackay got a bit closer to goal from a few yards further up, but not close enough.
That was about as good as it got for the Perth men in the opening period and it was the away side who came nearest to scoring in the last few minutes.
A long cross-field ball was met by Josh Magennis at the back post and his fellow Northern Irishman, Mannus, turned a well struck shot from an acute angle round the post.
Then from the corner Magennis volleyed a shot that had Mannus beaten but narrowly missed his left hand post.
Killie made a lively start to the second half as well.
On 49 minutes Rory Mckenzie’s skill at the right side of the penalty area earned him space to cross to the six yard box, from where Adam Frizzell headed over.
Things started to improve for Saints just after the hour mark when they eventually worked MacDonald thanks to a Wotherspoon volley that he tipped over.
Then from the corner MacDonald made a mess of a punch but it didn’t fall nicely for the Perth players.
On 66 minutes Tommy Wright made a double substitution, with strikers Steven MacLean and Chris Kane replaced by Graham Cummins and John Sutton.
The latter should have scored with his first touch but he couldn’t direct Wotherspoon’s low drilled cross on target.
Chris Millar had a goal-bound shot charged down and Saints now had real momentum for the first time in the game.
It would turn out to be a particularly miserable afternoon for Millar, who hobbled off near the end with another hamstring injury.
And he won’t have a Scottish Cup match to look forward to on his return as Killie were able to hold on to their narrow lead and see the game out.
They had MacDonald to thank for pulling off an incredible triple save from Sutton, Mackay and Cummins in injury time.