Reiging Super League champions Leeds Rhinos are 80 minutes away from the Grand Final after winning a thrilling sudden-death play-off tie in Perpignan.
The Rhinos twice came from behind to take the lead, but they could only breathe easy when a Danny McGuire drop goal three minutes from the end of a pulsating encounter put them two scores in front.
Stung by their humiliating defeat at Wigan seven days earlier, the Dragons made the liveliest start through their rampaging forwards but only had an eighth-minute try from departing full-back Clint Greenshields to show for all their early efforts.
Leeds gradually clawed their way into the game and were denied a score on 16 minutes when winger Ben Jones-Bishop had a try disallowed by video referee Phil Bentham for obstruction.
Back-to-back penalties then gave the champions a perfect attacking position and replacement hooker Shaun Lunt took full advantage. His delayed pass close to the line sent fellow substitute Stevie Ward over for a try on 34 minutes and two minutes later he supported a break by second rower Jamie Jones-Buchanan to cross for one himself.
Sinfield added both conversions to put his side into a 12-4 lead, but the Dragons cut the deficit to just two in the last minute of the first half when right winger Damien Blanch picked off a pass by McGuire and sprinted 90 metres for an opportunist try, goaled by Scott Dureau.
Blanch then put Catalan back in front eight minutes into the second half after collecting Dureau's pinpoint kick to the corner, but they suffered a blow when loose forward Gregory Mounis, whose offload had set up the tryscoring position, went off with an arm injury.
Trailing 14-12, Leeds looked to be heading for the exit but they struck back with two converted tries in another three-minute spell to seize control.
Centre Carl Ablett touched down Sinfield's grubber kick and McGuire scored his 201st Super League try after supporting a remarkable 50-metre break from forward Ryan Bailey.
Sinfield's fourth goal made it 24-14 but they paid the price for a series of defensive lapses as stand-off Thomas Bosc took Greenshield's pass to score the Dragons' fourth try, with Dureau kicking a second conversion.
Sinfield gave Leeds additional breathing space with a penalty eight minutes from the end but the Dragons, who put a limping Leon Pryce on for the last seven minutes, remained a threat until McGuire settled it with his one-pointer.
Final score Catalan Dragons 20 Leeds 27