A Christian Doidge hat-trick helped today's visitors Hibernian leave Perth with all three points.
Scott Allan was also on target for the Easter Road outfit with Stevie May scoring a late consolation for Saints.
The defeat leaves Tommy Wright's men in 11th place in a tightly packed Ladbrokes Premiership table, two points clear of bottom side St Mirren and just four points off the top six.
Saints went into this afternoon's fixture with Hibs on the back of two consecutive victories and full of confidence against a visiting side who had parted company with manager Paul Heckingbottom earlier in the week.
It was to be a horrendous start for the home side though as Christian Doidge put the visitors in front inside the first two minutes.
Lewis Stevenson's long ball forward found Flo Kamberi who had the beating of Saints captain Jason Kerr before squaring for Doidge who slotted home at the second time of asking after an initial stop from Zander Clark.
It was a nightmare start for Tommy Wright and his players and it nearly got worse just four minutes later.
Joe Newell found space at the edge of the area after a neat bit of play from Kamberi and his effort cannoned off Zander Clark's right-hand post denying Hibs a quickfire second.
It would get worse just ten minutes later though as the Leith side doubled their advantage.
Once again Kamberi was at the heart of it and his pin-point cross found Doige in the box who guided the ball past Clark to make it 0-2.
After that Saints began to find their feet in the match creating some half chances through Jason Kerr, Matty Kennedy and Scott Tanser.
However they were very nearly punished again after Jason Naismith's cross gave Doidge the opportunity to secure his hat-trick but the Hibs front man missed when it looked easier to score.
David Wotherspoon saw his effort blocked a few minutes later as Saints pushed for a goal to find their way back into the match but went in at half-time trailing 0-2.
That sparked the Manager into a half-time change with Drey Wright making way for Callum Hendry and Saints going for a 4-4-2 formation.
Once again though Tommy Wright's men shot themselves in the foot conceding a third minutes into the second half.
Matty Kennedy's misplaced pass was intercepted by Scott Allan who drove forward from the halfway line all the way through on goal before composing himself to slot home past Zander Clark with his left foot.
Saints tried to rally and Murray Davidson came close with a header but Chris Maxwell managed to save and hold from the midfielder's attempt.
Just before the hour mark Zander Clark was called into action, saving down low from Kamberi as Hibs pushed for a fourth.
And just one minute later they'd get it as Doidge made no mistake this time, heading home from 8-yards-out to seal his hat-trick and the match ball.
Matty Kennedy was replaced by Michael O'Halloran on the hour mark as Saints battled to try and get at least a goal from the match.
Anthony Ralston's low cross was played into the perfect area with Stevie May just inches away from connecting and getting hiimself on the scoresheet.
The impressive Kamberi came close with a curling effort before Ali McCann shot over the bar.
Jason Holt replaced David Wotherspoon and showed signs of what he brings to the team with a wonderful pass to Callum Hendry in the box but the striker's first touch let him down allowing Hibs to clear.
Doidge left the field to a standing ovation to be replaced by Martin Boyle before Scott Allan fired into the side-netting from the edge of the area.
Saints did manage to get a late consolation as Stevie May turned an Anthony Ralston cross home but it finished 1-4 on a disappointing day at McDiarmid Park.
SAINTS: Clark, Ralston, Tanser, Duffy, Kerr (c), Wright (Hendry 45), Wotherspoon (Holt 68), McCann, Davidson, Kennedy (O'Halloran 61), May
UNUSED SUBS: Parish, Vihmann, Swanson, Craig
SCORER: Stevie May (90)
HIBS: Maxwell, Naismith, Stevenson, Porteous, Hanlon (c), Slivka, Hallberg, Allan (Mallan 89), Newell (Horgan 89), Doidge (Boyle 81), Kamberi
UNUSED SUBS: Marciano, James, Jackson, Shaw
SCORERS: Doidge (2,17 & 58), Allan (47)
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