Caley Thistle struck late to move four points clear in second place, with Nikolay Todorov’s stoppage time winner securing a 3-2 Championship victory over Morton.
Inverness had taken a first half lead through Jordan White’s header, only for Aidan Nesbitt to pull the visitors level just after the hour mark.
The sides were only level for six minutes however, with Shaun Rooney restoring the Highlanders’ advantage, but Ton equalised for a second time through Reece Lyon on 77 minutes.
Just as it looked like Caley Jags had spurned the opportunity to strengthen their grip on second place, Todorov netted the hosts’ third header of the night in the dying moments to secure a vital three points for John Robertson’s men.
Inverness made three changes from the side which was defeated 5-3 by Hibernian in the Scottish Cup on Friday, with Lewis Toshney, Roddy MacGregor and Miles Storey drafted in to replace Aaron Doran, James Keatings and the suspended Brad Mckay.
Inverness forced Morton goalkeeper Danny Rogers into early action, with Jordan White seeing a header palmed over following a David Carson delivery, while the on-loan Aberdeen stopper did well to tip over Miles Storey’s strike from the edge of the box.
Inverness took the lead on 18 minutes when Rogers’ goal kick was intercepted by the home side shortly after the goalkeeper suffered a knock, before the ball was worked out to Walsh on the right, and his cross was sent into the corner by a thumping header from White.
Morton’s main goal threat came through on-form attacker Nicky Cadden, who saw a long-range effort comfortably held by Mark Ridgers before sending a curling free-kick just wide of the post.
The visitors continued to threaten after the break, with Cadden volleying over at the far post, while Jack Baird and Luca Colville off target with efforts from corners.
Morton’s breakthrough came on 61 minutes however, when Lewis Strapp’s delivery from the left picked out Nesbitt, who drilled a low effort through the legs of Ridgers to restore parity.
Caley Jags regained the lead just six minutes later however, with Carson’s free-kick picking out Rooney to nod a free header past Rogers.
Inverness pushed for a third, with Rogers making a fine double save to deny White’s deflected effort before the goalkeeper did well to thwart MacGregor’s follow up.
Morton grabbed their second equaliser on 77 minutes, with Craig McGuffie doing well to keep the ball in play to set up fellow substitute Lyon, who prodded home from six yards.