Hamilton Academical ended second-placed Dundee's nine-game unbeaten run to strengthen Ross County's grip on the First Division title and promotion to the top flight.
The visitors' defeat, combined with third-top Falkirk's surprise 2-0 loss at home to Morton, leaves County 15 points clear with only eight games remaining.
Yet it was Dundee who took the lead thanks to Ryan Conroy's convincing penalty after he was fouled by David Hutton in the 30th minute.
But Mark McLaughlin, who recovered from an injury picked up at the weekend to play, hit back for the Accies five minutes later, converting Daniel Redmond's corner from close range for his seventh goal of the season.
And Redmond turned provider again five minutes after the break when Jon McShane headed into the roof of the net from the midfielder's corner.
The result was put beyond doubt seven minutes later, when Mark Stewart's tidy finish found the corner of the goal.
Victory moves Accies into fourth place, five points behind Dundee and Falkirk, a point ahead of Partick Thistle, although the Glasgow side have a game in hand.
Hamilton: Hutton, Mensing, Canning, McLaughlin (Anderson 90), Kilday, Neil, Routledge, Redmond, McAlister, McShane (Spence 78), Stewart (Andy Ryan 83). Subs Not Used: Blair Currie, Gillespie.
Booked: Hutton, Redmond, Mensing.
Goals: McLaughlin 35, McShane 50, Stewart 56.
Dundee: Douglas, Irvine, McGregor, McKeown, Lockwood, McCluskey, McBride (Fotheringham 62), O'Donnell, Conroy, Hyde (Mcintosh 62), Bayne. Subs Not Used: Gibson, Chisholm, Benedictis.
Goals: Conroy 30 pen.
Ref: Alan Muir