Wigan were denied the derby spoils in a dramatic finish to an absorbing Super League clash.
When Thomas Leuluai struck a drop-goal in the closing stages, it edged Wigan into a 19-18 lead and it appeared it would be enough to settle a bruising encounter.
But in a cruel finish for the Warriors contingent, Saints swept down field and centre Mark Percival leapt to snatch a high-ball from Lewis Tierney’s grasp – and with it the win.
The run of results shows Wigan haven’t won in four league games, but there was a lot to admire from a derby which ebbed, flowed and frequently ignited.
In front of 13,138 fans, the Warriors led 14-6 and later 18-12, but they failed to close the game out as Saints - with ex-Warriors Matty Smith kicking superbly - roared back to secure a debut home victory for new boss Justin Holbrook.
Sixth-placed Wigan, who won the Good Friday derby 29-18, headed into the match one place and three points ahead of their fierce rivals.
As expected, Leuluai and Sam Powell returned to the Wigan ranks while Saints were unchanged from the side which battered Hull FC 45-0 last Saturday in new coach Holbrook’s first game in charge.
Wane was forced into one late change, when Joel Tomkins withdrew late with a groin strain and travelling reserve Callum Field was drafted in - the second time in three weeks he has not been named in the team and played, following a similar scenario at Swinton.
Armed-police where outside the ground as part of increased security measures - in wake of Monday’s attack - and there was an impeccably-observed minute’s silence before kick-off.
In baking evening sunshine, Saints made the brighter start. Full of energy and pace, they took a fourth-minute lead when Ryan Morgan out-jumped Liam Marshall to reach Smith’s angled kick. Percival’s conversion gave the home side a 6-0 lead.
But Wigan settled into their groove and dominated for large spells, scoring two tries to take a 14-6 lead.
First, they forced a repeat set - trapping lively Regan Grace behind his line - and Leuluai and Tierney combined slickly to send Tom Davies over. Williams marked his 100th game for Wigan with the conversion.
Wigan ramped up their defensive effort, with Sean O’Loughlin and Micky McIlorum harassing Saints’ forwards.
Williams poked Wigan further ahead with a penalty from Roby’s infringement in the tackle.
And then - with McIlorum off the pitch with a migraine - his replacement Sam Powell spotted a gap in Saints’ tiring defence to exploit, before finding jet-heeled Tierney in support. Williams’ goal opened up an eight-point lead but, just like at the Magic Weekend, Wigan faded when O’Loughlin was substituted and Saints took full advantage.
Again they crossed from a Smith kick, this time Zeb Taia crossing for a try which Percival converted. And the England centre had a chance to lock the score at half-time but his penalty effort was wide.
Wigan lost a second player before half-time - Liam Forsyth appeared to be sick on the pitch, and was taken down the tunnel.
Saints started the second-half smarter and sharper, and Wigan were forced to defend three successive sets on their line. When they did get possession, there was little respite, Frank-Paul Nuuausala turning over the ball and Wigan again forced to dig deep on their own line.
The visitors countered well, Williams and Marshall darting at a splintered defence, but after the returning O’Loughlin was held up by Roby, the set ended in a mess.
Approaching the hour-mark, there had still been no second-half score.
But Powell forced an error with a bone-jarring tackle on Grace, and moments later, a scramble for a loose ball ended with Saints prop Luke Douglas taking a knock and leaving the action.
Wigan couldn’t get over the line, but they persisted, and eventually it paid off when Williams threaded a kick into the ingoal, and the chasing Burgess managed to ground the ball before it dribbled over the dead ball line.
Williams couldn’t convert, and that miss presented Percival a chance to draw level with 13 minutes to go when he converted his own try from a Theo Fages offload. After so much strong defensive work, it was a soft score to concede, particularly as it stemmed from Willie Isas’s unnecessary foul-play.
Smith - a drop-goal master during his time at Wigan - attempted a one-pointer from 40m out, but missed.
Isa - energetic and aggressive throughout - redeemed his earlier blemish with a thunderous tackle which forced Taia to spill the ball and, from that position, Leuluai struck a sweet drop-goal to edge the Warriors 19-18 ahead.
A mass-brawl - sparked by Jon Wilkin’s hit on a grounded Tierney - went unpunished by referee Phil Bentham.
And Saints stropped down field to take a dramatic lead, Percival snatching the ball from Tierney’s grasp - after he had appeared to have defused a high kick - to cross. In a cruel finish, Tierney knocked on to end any hopes of a late escape act.
St Helens: Makinson; Swift, Percival, Morgan, Grace; Fages, Smith; Walmsley, Roby, Amor, Taia, Wilkin, Knowles. Subs: McCarthy-Scarsbrook, Douglas, Thompson, Lee.
Wigan: Tierney; Davies, Forsyth, Burgess, Marshall; Williams, Leuluai; Nuuausala, McIlorum, Sutton, Isa, Farrell, O’Loughlin. Subs: Davies, Powell, Tautai, Wells.
Referee: Phil Bentham
Starman: Sam Powell