CHRIS Kane grabbed a winner for St Johnstone with six minutes remaining as 10-man Caley Thistle went down 1-0.
Kane popped up at the back post to give the Saints all three points in a game where a determined Inverness side looked to be holding out for a draw.
David Wotherspoon had his spot kick well saved by Fon Williams with 22 minutes to go, in an incident which saw Gary Warren sent off.
Warren had brought down Danny Swanson just inside the area and was carded for the second time. However, his goalkeeper was able to bail him out.
Just when the visitors thought they had weathered the storm, Kane crept in to give Tommy Wright's side's push for a top-six spot a jolt .
It means Caley Thistle, who will have just Danny Devine as a recognised centre-back for Saturday's game with Hamilton Accies, as Carl Tremarco is also suspended and Josh Meekings is not fit, remain in 9th spot.
Nat Wedderburn came on for the last 17 minutes in Perth and will be a prime contender to step into an already-depleted backline, with David Raven still out and Lewis Horner not 100 per cent.
John Hughes' squad was depleted further with the loss of Miles Storey and Sunday's Scottish Cup hero Andrea Mbuyi-Mutombo, both of whom were laid low by flu. It meant a first start for Liam Hughes up front alongside Jordan Roberts.
It was the latter who missed a glorious opportunity to break the deadlock with just three minutes on the clock. Hughes teed up Liam Polworth on the right and his arching cross bisected the corridor between defenders and goalkeeper. Roberts steamed in unmarked at the back post but headed over the crossbar.
The hosts had their first attempt on goal 11 minutes in after Steven MacLean did well, holding off Tremarco and feeding the on-rushing Darnell Fisher. With time and space to pick his spot, the on-loan Celtic defender blazed his effort high over the top.
On a far from ideal surface at McDiarmid Park, neither side threw much at each other in the opening 25 minutes. Iain Vigurs whistled a free kick over Alan Mannus' goal but there was little for makeshift frontman Hughes to feed on.
Bar the odd cross into the box, the Saints looked threatening on precious few occasions and at times were content to allow Caley Thistle possession of the ball. Players were making runs in behind for the Caley Jags but the final ball through to them was often locking.
A tepid first half closed with the first save either goalkeeper had to make in the opening period. Simon Lappin's free kick was punched behind by Fon Williams and from the resulting corner, Joe Shaughnessy headed straight at the Wales international.
Two early chances in the second half were dragged wide by Polworth and Roberts as Inverness sought to end a run of four games without a win, all of them on the road. Sloppiness was setting in at both ends, with Warren lucky to avoid conceding a penalty for barging over Kane and Wotherspoon atoning for a poor clearing header by denying Danny Williams.
The game was gradually becoming more open after a period where the traded tackles rather than chances. Polworth fired a rasping drive over after being fed by Roberts while at the opposite end, Wotherspoon was denied by blocks from Danny Devine and Williams.
St Johnstone had a fantastic chance to take the lead on 68 minutes as Warren was this time punished, rightly, for cleaning out Swanson and picked up his second booking in six minutes. The 10 men could have been coming from behind but for Fon Williams, who dived to his right to keep out Wotherspoon's effort and Tremarco was on hand to block the rebound.
It became a backs-to-the-wall job for the Caley Jags after that, with Fisher, Murray Davidson and Wotherspoon all having opportunities to get the opening goal.
But it finally came on 84 minutes when Fisher sold Tremarco a dummy on the right side of the area before teeing a ball up to the back post. Those in white failed to clear and Kane was on hand to prod in.
Inverness failed to threaten the Saints goal in response, with a home game on Saturday a welcome boost after five games on the road.
ST JOHNSTONE: Mannus; Fisher, Scobbie, Anderson, Shaughnessy, Swanson (Craig, 87), Davidson, Lappin, Wotherspoon, Kane, McLean (Cummins, 83). Subs unused: Clark, Doyle, Sutton, Thomson, Krachunov. Booked: none.
CALEY THISTLE: Fon Williams; Warren, Devine, Tremarco, Polworth (Horner, 88), Draper, Tansey, F. Williams, Vigurs, Roberts (Wedderburn, 73), Hughes. Subs unused: Esson, R. Williams, Foran, Brown, MacLennan. Booked: Roberts, Warren., Tansey. Sent off: Warren.
Referee: D. Robertson.