Caley Thistle fell to their third straight league defeat, with their 1-0 loss against Hamilton Accies leaving them just five points above Kilmarnock in the relegation play-off position.
Despite Inverness enjoying much of the possession and creating several chances, Carlton Morris’ second-half strike was enough to secure the points for the Lanarkshire side, who moved level with John Hughes’ side in the table.
Caley Thistle were forced into two defensive changes from the side that went down 1-0 against St Johnstone on Wednesday, with skipper Gary Warren and Carl Tremarco ruled out through suspension, the pair being replaced by Lewis Horner and Nat Wedderburn.
Accies also made two changes for the trip to the Highlands, with Greg Docherty and Grant Gillespie replacing Darren Lyon and Ali Crawford from the side that went down 1-0 against Motherwell the previous week.
Inverness were first to threaten on 15 minutes, when good work from Liam Hughes allowed stand-in skipper Greg Tansey to run through on goal, before he squared for Liam Polworth, who drilled over from 20 yards.
Caley Jags were once again on the attack just two minutes later, when Polworth set up Jordan Roberts for an effort, but he struck just over.
It had been a bright start but Accies had their first sniff of goal on 22 minutes when Gramoz Kurtaj drilled the ball wide from the edge of the box.
Although it was not a first-half of many chances there was enough reason for encouragement for the hosts, and they made a bright start to the second-half, with Iain Vigurs failing to direct Danny Williams’ delivery on target, before Polworth appealed for a penalty under a challenge from Greg Docherty.
It looked as if Inverness were beginning to dictate but against the run of play they were left stunned when Accies grabbed the lead, as Grant Gillespie picked out Carlton Morris, who drilled in off the post from a wide angle 10 yards from goal, with Inverness claiming furiously for a foul on Horner in the build-up.
It came as a blow to the hosts, who desperately tried to force their way back into the game, with Tansey fizzing a 30-yard free-kick just over.
Hughes went all out to salvage something from the game, bringing on Storey and Richie Foran in attack, but Inverness had to call upon goalkeeper Owain Fon Williams to keep them in the game when he made an excellent to deny Docherty with a low drive on 81 minutes.
Caley Jags upped their threat in the dying minutes, with Wedderburn striking the post following a goalmouth scramble, before Liam Hughes volleyed wide from the edge of the box.