Inverness claimed a second straight Scottish Premier League win as Hearts were beaten in the Highlands.
Hearts' Jamie Hamill struck the bar with a long-range effort and Inverness defender Kenny Gillet had a goal ruled out for offside before the break.
But Shane Sutherland broke the deadlock for the hosts after the break, heading home Jonny Hayes' cross.
David Templeton had a penalty appeal turned down and John Sutton fired wide as Hearts pressed for an equaliser.
Terry Butcher's side remain eight points ahead of bottom club Dunfermline and are now seven clear of Hibernian.
Hearts stay third, but the Edinburgh side are joined on the same number of points by St Johnstone and Motherwell.
Doubts about whether the match would go ahead following inclement weather earlier in the day were overcome as conditions improved in the run-up to kick-off.
Hamill's early strike from 35 yards thundered against the crossbar before Inverness began to assert themselves in the first half.
A free-kick by Tansey was saved by Marian Kello and the goalkeeper then stooped low to block an effort by Richie Foran.
Templeton tested Ryan Esson from 25 yards, the Inverness keeper doing enough to keep the shot out.
Inverness went back on the attack and Kello saved attempts by Hayes and Sutherland in quick succession before Gillet netted the second rebound only to be frustrated by the assistant referee's flag.
Nick Ross flashed a swerving 25-yard shot wide and Gregory Tade was also off target for the hosts before the break.
But their pressure told in the 49th minute as Sutherland got on the end of Hayes' centre and nodded powerfully towards goal, Kello unable to stop the ball crossing the line.
Hearts responded with Ian Black's long-range free-kick, which required a save from Esson.
Sutherland's cross almost caught out Kello as it rebounded off the post before Hearts substitute Suso Santana went close from distance.
Tansey played in Hayes as the match entered its final 10 minutes, but the winger was foiled by Kello.
With time running out, the visitors pushed for parity and Rudi Skacel's shot was inches over.
Templeton then went down in the box following a challenge by Josh Meekings, but referee George Salmond allowed play to continue.
Sutton's late effort was past the post, meaning Hearts lost their first match since early December.