A try from Samoan star Paul Williams two minutes from time saw Stade Francais edge English club Exeter 22-17 on Thursday to advance to the semi-finals of the European Challenge Cup. Stade, last year\'s losing finalists, ultimately proved too strong for a plucky Exeter side despite failing to dominate the game. Exeter fly-half Ignacio Mieres opened the scoring with a 20th minute penalty after the home side strayed offside at a ruck. The Argentinian missed his second effort but then saw counterpart and compatriot Felipe Contepomi sin binned soon after for reacting to a bone-crunching hit by hooker Chris Whitehead with a wild, swinging punch. Mieres kicked the ensuing penalty, but Julien Dupuy clawed one back for Stade after a reckless tackle by Exeter winger Gonzalo Camacho. The respective kickers then traded penalties to leave the half-time score at 9-6 and the game delicately poised with each team failing to find their rhythm. Stade came out firing on all cylinders in the second period, a dink through from Contepomi eluding the covering Phil Dollman but falling nicely for Djibril Camara, the full-back stretching to dot down in the corner for the game\'s first try. Dupuy missed the conversion but hit a penalty in the 48th minute, cancelled out immediately by Mieres. The France international scrum-half was on target again to stretch Stade\'s lead to 17-12. But with 11 mintues remaining, missed tackles from Contepomi and Dupuy allowed Exeter\'s Fijian centre Sireli Naqelevuki in for a soft try, Mieres missing the conversion to leave the scores tied. The Argentinian, a former Stade player, then crucially missed a snatched drop-goal. The Parisians came roaring back up the pitch and Dupuy found a gap and sent out an inch-perfect pass to the fast-approaching Williams for the decisive try. On Friday, defending champions and current English Premiership leaders Harlequins face a tough away game to the Jonny Wilkinson-led Toulon on the French Mediterranean coast. Wasps host Biarritz on Saturday, with Brive entertaining Scarlets on Sunday in the final quarter-final.