Clayton Oliver shone against his former team and GWS racked up successive wins for the first time this AFL season, continuing Melbourne's barren Alice Springs run.
Backing up from their 14-goal third term against Brisbane last week, the Giants' Orange Tsunami also overwhelmed the Demons late on Sunday in the 19.5 (119) to 9.16 (70) win. GWS kicked 10 goals to three in the second half.
Melbourne won the inside-50s 62-46 and also were ahead in contested possessions and clearances - key numbers that normally equate to success.
But coach Steven King was left lamenting some terrible clangers that, combined with the Giants' goalkicking accuracy, doomed Melbourne.
In his first game against the Demons, Oliver only had two possessions to quarter-time and Jack Steele was winning their midfield match-up.
