A late winner from Steven Lawless gave Partick Thistle a deserved 1-0 victory against a below-par Caley Thistle at Firhill.
The hosts had the better of the play and chances during a low key encounter but struggled to trouble the Inverness defence until Lawless rifled a low shot home from the edge of the area six minutes from time.
The defeat means John Hughes’ side remain seven points above fourth-placed Dundee United having played one game more.
Inverness made one alteration from the team that defeated Raith Rovers 1-0 in the Scottish Cup quarter-finals with Edward Ofere dropping out at the expense of Gary Warren, who returned from a two-game suspension.
The Caley Jags lined up in an unusual 5-4-1 formation with Graeme Shinnie and David Raven deployed as wing backs and Ryan Christie and Danny Williams providing the support for lone forward Marley Watkins.
Partick, who had scored eight times in their previous three matches against Inverness, stuck with the same starting XI that ran out 3-0 winners against St Johnstone last weekend.
The visitors should have opened the scoring with only nine minutes on the clock but Watkins fluffed his lines after good work by Raven.
Undeterred, Inverness continued on their pursuit of the first goal with Josh Meekings crossing for Ryan Christie but Scott Fox was equal to the Inverness attacker’s diving header.
Partick also had their chances during a scrappy opening period with James Craigen’s low drive kept out by an excellent Ryan Esson stop.
A powerful Ryan Stevenson free kick stung the palms of Esson as Partick made a positive start to the second half.
It was one-way traffic with Inverness camped in their own half for long periods but Partick were struggling to turn possession into penetration.
Inverness were in need of some inspiration and introduced Tarmo Kink for Christie to provide a different attacking threat with Williams making way for Aaron Doran soon after.
But it was the Maryhill men who struck late on when Lawless latched onto a Lyle Taylor knockdown and slotted the ball beyond the despairing Esson.