Queen of the South stunned First Division leaders Morton with a first-half deluge of goals.
Kevin Smith applied the finishing touch to Stephen McKenna's header to put Queens ahead on 20 minutes and Tom Brighton headed the hosts' second.
Smith headed home Allan Johnston's cross and completed his hat-trick with a 20-yard shot in the 38th minute.
Peter MacDonald fired a late consolation for Morton but it did little to detract from Queens' win.
Queen of South:
Robinson, Craig Reid, Campbell, McGuffie,Higgins, McKenna, Simmons, McLaughlin, Brighton (Clark 61), Smith (Holt 83), Johnston (Carmichael 66). Subs Not Used: Black, McKenzie.
Smith 20, Brighton 30, Smith 35, 38.
Stewart, Graham, Evans, McCaffrey, Forsyth, Di Giacomo, Smyth, Tidser (Fitzharris 56), O'Brien (Bachirou 56), MacDonald, Jackson (Weatherson 51). Subs Not Used: McGeouch, Deans.