First Division leaders Morton were humbled at home by bottom side Dumbarton.
Sons goalkeeper Jamie Ewings denied Scott Taggart and Peter Weatherson before Garry Fleming fired the visitors ahead.
Scott Agnew directed James Lister's cross past Morton goalkeeper Derek Gaston to double Dumbarton's lead before the break.
And Bryan Prunty's strike 11 minutes from the end completed the scoring as the hosts suffered their first defeat since November.
Morton: Gaston, Reid (O'Ware 88), Rutkiewicz, Mark McLaughlin (Wallace 46), Dyer, Bachirou, Hardie, Tidser, Taggart, Weatherson (MacDonald 46), O'Brien. Subs Not Used: Hutton, Wilkie.
Dumbarton: Ewings, Devlin, Graham, Lithgow, Forsyth, Gilhaney (Lamont 88), Turner, Agnew, McDougall, Fleming (Prunty 75), Lister (McCusker 83). Subs Not Used: Grindlay, McNiff.
Booked: McDougall, Lister.
Goals: Fleming 32, Agnew 39, Prunty 79.
Ref: John Beaton