Gregory Tade's early strike was enough to hand Inverness victory over Aberdeen as the visitors held out with 10 men.
Billy McKay rounded home goalkeeper Jason Brown before setting up Tade in front of goal after 10 minutes.
Kari Arnason cleared a Richie Foran effort off the line as Caley Thistle dominated the first half.
The Dons rallied, but they could not make 45 minutes of pressure tell despite Josh Meekings's 58th-minute dismissal for a second yellow card.
And it officially ended the home side's hopes of catching Hearts to finish in the Scottish Premier League's top six.
Mitch Megginson replaced Rory Fallon in the Dons forward line, with the New Zealand international dropping to the bench.
Owain Tudur Jones returned to the midfield for Inverness, without a win in seven matches, with on-loan Wolves striker Sam Winnall having to settle for being a sub.
Terry Butcher's side lost goalkeeper Ryan Esson with an injury picked up during the pre-match warm-up and was replaced with Jonny Tuffey.
The Northern Ireland international was under immediate pressure and clawed away a Rory McArdle cross, with Gavin Rae slicing wide from the corner.
However, it was Inverness who took the lead when McKay pounced on Tade's head-flick before rounding Brown and sending his low cross from the bye-line into the unmarked Frenchman's path a mere two yards from goal.
Scott Vernon failed to make the most of space allowed him on the edge of the Inverness box and fired weakly at Tuffey and McKay also failed to find the right power and direction at the other end with a shot across the face of goal.
Caley Thistle were denied a second by Arnason's goalline clearance following Foran's low drive from 12 yards as the ball bobbled about the home penalty box.
Having been hesitant and lacklustre, Aberdeen came out fired up after the break and created more in the first couple of minutes than they had in the whole of the opening 45 as the ball pinged around the Caley Thistle penalty area.
The visitors were fortunate not to concede a free-kick on the edge of their own box when Graeme Shinnie slipped and controlled the ball on the ground with his hand.
Their luck was out seconds later when Meekings was shown a second yellow card after a late challenge on Vernon.
The Dons were piling on the pressure without creating clear-cut chances and were fortunate when Tade mis-hit from just inside the box after a rare dangerous break from the visitors.
Caley Thistle were also left short-handed in the dugout when assistant Maurice Malpas was sent to the stand after a touchline protest as the Dons continued to press.
However, they were thankful for Tuffey's strong fists as the goalkeeper parried clear a 16-yard drive from substitute Mohamed Chalali.