Match ends, Livingston 1, St. Mirren 3.
St Mirren moved six points clear of Scottish Premiership bottom-club Dundee after a comeback win over 10-man Livingston.
Victory in West Lothian moved the Paisley side to within two points of 10th place Hamilton and safety.
Scott Robinson opened the scoring for the hosts, shortly after Livingston's captain Craig Halkett was sent off.
Paul McGinn equalised, before Danny Mullen and Simeon Jackson struck after the break.
Two goals in two minutes in the second-half swept Livingston aside, with St Mirren the only side in the Premiership's bottom three to win.
Lions undone by former Livi striker
Livingston went into the post-split fixtures with the luxury of setting themselves relaxed, end-of-season targets rather than fraught ones that involved securing Premiership safety.
Manager Gary Holt is urging his men to make seventh spot theirs and not let the campaign fizzle out, so they were irked at being reduced to 10 men less than a quarter of the way into the match.
Was Halkett the last man when he challenged Lyons? Did he get anything on the ball? It was hard to tell conclusively without the help of replays.
Nevertheless, referee Willie Collum was booed by the home fans as he entered the tunnel for half-time, his decision clearly not appreciated.
But at least the call sparked the game into life, albeit not in the way you would have expected after the home side had been reduced to 10 men.
Livi cut through the Saints defence brilliantly, although with frightening decisiveness if you were an away supporter. Steven Lawless teed Robinson up for his second goal of the season.
The Lions' lead did not last long. Paul McGinn must have witnessed the hosts' goal and thought he could go one better - gliding down the right, exchanging passes with Anders Dreyer before squeezing his shot under goalkeeper Liam Kelly.
Hamilton Accies, above them in the league, were not winning. Dundee, below them in the league, were losing. But for a long time in the second half, it looked like the Buddies were going to struggle to summon the extra bit of quality required to take a massive three points.
However, a former Livi striker stepped up to produce the goods. Mullen ruthlessly netted his fifth of the season from the edge of the box when Kyle Magennis found him.
Cue hysteria in the away support, and even more two minutes later when Jackson was well placed to feed on the scraps as Livi goalkeeper Kelly spilled Kyle McAllister's low drive.
Analysis - BBC Sport Scotland's Kenny Crawford
This is a huge result for St Mirren, in terms of points gained on rivals, but also a gigantic psychological boost.
The Paisley club's players can take real confidence from being able to step up to the plate and deliver three points when anything less would have been unacceptable, given they were playing against 10 men for the majority of the match.
That detail will likely be what the Livi manager takes issue with, but his charges coped well and can be satisfied how long they stayed in the contest on an energy-sapping afternoon in the sun.
'We have to take it on the chin' - Reaction
Gary Holt, Livingston manager - "To a man I thought our guys were excellent, the shift they put in was really good and we had chances with 10 men and if it was 11 v 11, I think we'd have won the game.
"We countered them well in the first half, but it's always going to be tough when at half time they changed it and brought extra attackers on and made the game bigger. But I thought we were comfortable.
"The second takes the stuffing out of you, especially when you've played so long and I feel for the lads because they put in a shift. But we just have to take it on the chin."
Oran Kearney, St Mirren manager - "The key thing above anything else today was to come away with the three points and we're happy we've done that.
"I have to give them credit for the character that they've shown, to go ahead on days like this can be tough to see the games out but to come from behind and the manner we did it speaks volumes for the group.
"We've been in a good place for six weeks and really have gained momentum, built on performances and accumulated points so we want to keep that rolling and big performances coming.
"But come Monday it'll be all systems go for next week again."
- 26HalkettBooked at 17mins
- 9HardieSubstituted forMengaat 73'minutes
- 15LawlessSubstituted forOdoffinat 23'minutes
- 10SibbaldSubstituted forLamieat 52'minutes
- 23De Vita
- 6MacKenzieSubstituted forJacksonat 45'minutes
- 14LyonsSubstituted forMcAllisterat 63'minutes
- 39ErhahonBooked at 52minsSubstituted forMagennisat 76'minutes
- William Collum
- Shots on Target
Second Half ends, Livingston 1, St. Mirren 3.
Attempt missed. Daniel Mullen (St. Mirren) right footed shot from the left side of the box is high and wide to the right.
Foul by Ryan Flynn (St. Mirren).
Scott Pittman (Livingston) wins a free kick on the right wing.
Attempt missed. Keaghan Jacobs (Livingston) right footed shot from outside the box is just a bit too high from a direct free kick.
Foul by Jack Baird (St. Mirren).
Dolly Menga (Livingston) wins a free kick in the defensive half.
Paul McGinn (St. Mirren) wins a free kick on the left wing.
Foul by Dolly Menga (Livingston).
Simeon Jackson (St. Mirren) wins a free kick in the defensive half.
Foul by Scott Pittman (Livingston).
Corner, Livingston. Conceded by Václav Hladky.
Corner, Livingston. Conceded by Ryan Flynn.
Attempt missed. Declan Gallagher (Livingston) header from the centre of the box is just a bit too high following a set piece situation.
Foul by Stephen McGinn (St. Mirren).
Scott Pittman (Livingston) wins a free kick in the defensive half.
Goal! Livingston 1, St. Mirren 3. Simeon Jackson (St. Mirren) right footed shot from the centre of the box to the bottom right corner.
Attempt saved. Kyle McAllister (St. Mirren) left footed shot from outside the box is saved in the centre of the goal.
Goal! Livingston 1, St. Mirren 2. Daniel Mullen (St. Mirren) right footed shot from outside the box to the bottom right corner. Assisted by Kyle Magennis.