The destiny of the points still seemed in the melting pot at the half way point - even though the fiery Dragon were full value for their 8-0 lead - but the Super League leaders then wilted in the red-hot Mediterranean temperature and were shot to pieces by a six-try salvo.
A first-half head wound to skipper Paul Wellens following a collision with team-mate James Roby didn’t help their cause and this was compounded when they lost Jonny Lomax, on his return to the set up, in the 64th minute with a season-ending knee problem.
But coach Nathan Brown refused to blame injuries or the sweltering heat for Saints fourth league defeat of the season.
He said: “We can’t use that as a excuse but obviously we out on our feet at the end.
“We also paid a fair price for our first-half efforts but defensively our commitment for each other needed to be better regardless of fatigue.
“It was also one of the few occasions this year when our attacking play wasn’t so good, putting a lot of unnecessary pressure on our defence and towards the back end we were unable to cope.
“We will now go through the video, talk to the players as a group and as individuals. We can’t brush it off and hope it turns around.
“We have to dust ourselves down and give our home fans something to cheer against Castleford on Sunday.”
Saints destroyer-in-chief proved to be speedy winger Michael Oldfield who roared in for a hat-trick of tries as the Dragons upturn in form continued, thanks to the silky skills of former Saints’ playmaker, Leon Pryce.
The hosts snatched an early lead when Thomas Bosc’s high kick was knocked on by Tommy Makinson and Vincent Duport collected the ball and touched down in the corner.
Two minutes later, Makinson had a try ruled out as Paul Wellens’ pass was deemed to have gone forward, but on the stroke of half-time the French side doubled their tally - and again it came from a tantalising kick by Pryce, allowing Oldfield to outjump Matt Dawson to score.
Crucially the hosts were first to strike on the resumption through Duport with Bosc adding his first conversion to extend the lead to 14-0.
Just after the hour mark the Dragons surged further ahead, Henderson powering over from close range after good work by Jeff Lima.
It virtually ended Saints’ resistance as the Dragons wrapped up the points thanks to further tries from Bosc (68 mins), Oldfield (70 mins and 80 mins), Daryl Millard ( (76 mins).
The game also ended in a frustrating manner for St Helens substitute Alex Walmsley who was sent to the sin-bin along with Elio Petissier for fighting.