Bristol's Premiership status took a step beyond the tenuous on Sunday after they let a 14-10 lead against Harlequins slip in the Guinness Premiership.
England wing Ugo Monye broke Bristol hearts by sinking the Guinness Premiership relegation favourites with an injury-time try.
Monye, a second-half substitute, struck after Bristol went 14-10 ahead through a 73rd-minute penalty try.
It denied the Premiership's bottom club only their second league victory of the season as they began life without Richard Hill.
A battling display at the Memorial Stadium saw Bristol move ahead after wing David Lemi was barged off the ball as he chased a kick behind Quins' line.
Hill, whose six-year reign as head coach ended on Friday, has seen his long-time assistant Paul Hull take over in the coaching hot seat.
And while Hull looks as though he will be presiding over a National League One club next season unless his players can muster an unlikely fightback, he can take heart from a committed effort.
A losing bonus point proved scant reward from a game that leaves Bristol 12 points behind 11th-placed Worcester with just seven Premiership fixtures left.
Bristol led at half-time thanks to a converted Neil Brew try, but England wing David Strettle's touchdown within two minutes of the restart edged Quins ahead.
And they just did enough to shade the contest, claiming a win which lifts them into fourth place above Leicester and Bath.
Bristol suffered an unsettling start, losing fly-half Adrian Jarvis in the third minute with a leg injury as Quins monopolised possession, freeing wings Strettle and Tom Williams at regular intervals.
But the Bristol defence, despite being stretched, denied Quins during an opening quarter the visitors dominated in terms of territory.
And Bristol then stung the visitors by scoring a try from their first notable attack.
Wing Lee Robinson's powerful break scattered three Quins defenders, and when the ball was moved wide, hooker David Blaney delivered a scoring pass to Brew.
Barnes' touchline conversion made it 7-0, but Quins responded within eight minutes when former England scrum-half Andy Gomarsall sent hooker Gary Botha on a 15-metre run to the line.
The South African bundled Bristol scrum-half Shaun Perry out of his path, claiming a try that brought Quins back to within two points, yet their early fluency had been stalled by Bristol's impressive organisation.
Malone missed the conversion before Barnes rifled a penalty wide, but with number eight Dan Ward-Smith enjoying a productive game in the loose, Bristol continued to generate momentum.
And a 7-5 interval lead was a deserved reward, given they had nullified the threat of Quins' early wide game by making their tackles count.
Quins though, required little time to wipe out Bristol's lead, moving ahead in the 42nd minute when Perry spilled possession inside his own 22, Malone sending Strettle sprinting away.
Neither side could establish a firm grip on the contest and with the scrums proving a mess for referee Chris White, his patience finally snapped 12 minutes from time.
Bristol tighthead prop Darren Crompton and his opposite number Ceri Jones were both sin-binned, but the home side then went ahead seven minutes from time.
Lemi, comfortably the biggest attacking threat in either side, launched a superb kick and chase to the corner.
He was denied the touchdown, yet White awarded a penalty try on the recommendation of his assistant after a Quins player pushed Lemi as the Samoan attempted to touch down.
Barnes added the extras, and then it was a case of whether or not Bristol could keep their nerve and preserve a four-point lead.
It was no surprise that a team short on confidence could not quite manage it, as Monye struck the killer blow before Malone converted and lifted the Londoners into play-off territory.
Tries: Brew, penalty try
Con: Barnes 2
Tries: Botha, Strettle, Monye
Bristol: 15 Tom Arscott, 14 Lee Robinson, 13 Neil Brew, 12 Luke Eves, 11 David Lemi, 10 Adrian Jarvis, 9 Shaun Perry, 8 Dan Ward-Smith, 7 Joe El Abd (capt), 6 Redford Pennycook, 5 Nathan Budgett, 4 Dave Attwood, 3 Darren Crompton, 2 David Blaney, 1 Mark Irish.
Replacements: 16 Scott Linklater, 17 Wayne Thompson, 18 Roy Winters, 19 Alfie To'oala, 20 Haydn Thomas, 21 Ed Barnes, 22 Nathan Brew.
Harlequins: 15 Mike Brown, 14 David Strettle, 13 Gonzalo Tiesi, 12 Jordan Turner-Hall, 11 Tom Williams, 10 Chris Malone, 9 Andy Gomarsall, 8 Tom Guest, 7 Will Skinner (captain), 6 Chris Robshaw, 5 George Robson, 4 Ollie Kohn, 3 Mike Ross, 2 Gary Botha, 1 Ceri Jones.
Replacements: 16 Aston Croall, 17 Mark Lambert, 18 Jim Evans, 19 Neil McMillan, 20 Junior Poluleuligaga, 21 Nick Evans, 22 Ugo Monye.
Referee: Chris White
Touch judges: Robin Goodliffe, Stuart Terheege
Assessor: Ed Morrison
Television match official: Matt Peters