Jones set up two of Catalans' tries
Catalans Dragons: (4) 21
Tries: Khattabi, Murphy, Croker, Greenshields
Goals: Jones 2
St Helens: (0) 0
Catalans Dragons pulled off a big upset by beating Super League leaders St Helens in Perpignan.
The Dragons ran in four tries without reply to boost their hopes for the Challenge Cup final later this month when they will meet Saints at Wembley.
Stacey Jones orchestrated the victory, kicking two of four goal attempts and adding a drop goal.
His neat grubber kick put in Younes Khattabi for the first try and he played in Justin Murphy for the second.
Leeds had drawn level on points with St Helens at the top of the table with victory over Salford on Friday but a win over struggling Catalans would have restored Saints' cushion.
The visitors had several chances in the first half but Willie Talau was having one of his less inspiring days and the Dragons took full advantage.
And luck was on their side, too, with the hosts perhaps fortunate to escape unpunished after holding back Paul Wellens.
Catalans' third try came from Jason Croker and owed much to some slack defending, Jason Cayless missing a tackle and Talau unable to catch his man.
Catalans had another score disallowed by the video referee but Clint Greenshields added the fourth and final try before Jones added a drop goal.
Catalans Dragons: Greenshields, Murphy, Wilson, Raguin, Khattabi, Jones, Mogg, Chan, Quigley, Guisset, Gossard, Croker, Mounis.
Replacements: Ferriol, Casty, Touxagas, K. Bentley.
St Helens: Wellens, Gardner, Gidley, Talau, Meli, Long, Graham, Cunningham, Cayless, Eastmond, Bennett, Flannery, Wilkin.
Replacements: Hargreaves, Roby, Fa'asavalu, Clough.
Referee: P Bentham (Warrington)