The Dons showed their clinical side as they punished the home side on the counter-attack and three points takes them alongside Celtic and Hibernian, though both play on Sunday.
Johnny Hayes fired a low shot beyond Craig Samson to open the scoring after 10 minutes and the in-form Niall McGinn doubled the visitors' lead on the stroke of half-time, ending a lightning-fast counter by slamming the ball high into the net.
Chris Clark drilled a low shot past Samson with four minutes remaining to put the game beyond Saints before late strikes from Mark Reynolds and Steven Thompson rounded out the scoring.
The visiting captain's spot-kick in the 90th minute cancelled out Owain Tudur Jones' 30-yard thunderbolt opener, which came in the 19th minute at Tulloch Caledonian Stadium.
The draw extended Inverness's unbeaten run to 10 games in all competitions.
It is likely to do little to ease the the woes of Hearts, who might have played their last away game if the club succumbs to a winding-up order over a tax bill of almost £450,000.
Two goals from Paul Heffernan, making his first start of the season after recovering from a dislocated shoulder, and a superb strike from Gary Harkins had the Rugby Park fans celebrating after two home defeats.
Dundee provided further evidence that they could mount a serious fight against relegation as Nicky Riley's strike earned them a 1-1 draw against Motherwell.
Riley struck against the run of play before Motherwell finally made their first-half dominance count in injury-time when Michael Higdon followed up after Rab Douglas had stopped Henrik Ojamaa's shot.
The visitors refused to buckle though and survived intermittent spells of second-half pressure, which included a disallowed goal from Higdon, while showing a touch of menace on the break.