Stephen Donald won the duel of the Kiwi fly-halves to earn Bath a stirring 21-18 victory and inflict a third Aviva Premiership defeat on league leaders Harlequins.
Donald turned in his best performance for Bath by kicking seven penalties from eight attempts but it was nip and tuck all the way through against fellow New Zealander Nick Evans, whose boot was also responsible for all his side's points.
Bath's never-say-die spirit was typified by former Scotland number eight Simon Taylor who led a monumental effort in the loose to blunt Harlequins dynamic attack.
Quins had won their last three meetings with Bath, including a 21-12 victory in the LV= Cup tie a week ago. The match winner that night at The Stoop was fly-half Ben Botica but Evans had recovered from an ankle injury to claim back his number 10 shirt.
The Recreation Ground was in remarkably good condition although the River Avon was in full flood, overflowing the footpath behind the main stand.
Evans wasted no time in pinning Bath back into the corner and the pressure brought a succession of penalties, eventually allowing the New Zealander to open the scoring.
Nick Abendanon's counter-attacking verve earned Donald a chance at the other end but the World Cup winner was off target. Bath continued to wage a fierce battle on the gain-line and were rewarded on 16 minutes when Donald chipped over a penalty in front of the Quins posts to level at 3-3.
They should have extended the lead shortly afterwards when Matt Banahan charged down a Tom Williams clearance and regathered the ball, only to fire an uncatchable pass at centre Semesa Rokoduguni.
Back came Quins, Evans pulling the strings to fashion an opening for Nick Easter but Jordan Turner-Hall was bottled up when he threatened to burst free. Bath infringed and Evans knocked over a 23rd minute penalty.
But it was the home side who finished the half strongest, despite being at a clear disadvantage in the scrums. They made up for that with a strong line-out performance and plenty of aggression in and around the tackle area. That effort was replicated in the backline with strong running from the likes of Banahan and Tom Biggs.
Donald punished a ruck infringement with a kick from 35 metres and was then successful with a 50-metre effort to send his side in at half-time with a 9-6 lead.
Quins began the second half hesitantly and Dickson sliced a box kick into touch. Mark Lambert earned a warning for taking out Simon Taylor in the line-out and Donald kicked his fourth penalty.
After Evans missed a straightforward chance to pull back three points Quins earned a penalty and scrum-half Karl Dickson sped away only to be caught on the line by Guy Mercer. The visitors fancied their chances at a series of reset scrums but Bath held their nerve and Evans eventually had to be content with a 56th minute penalty.
A late challenge by Mercer on Evans, duly punished by the Kiwi, brought the Londoners level on the hour but Bath were back in the lead four minutes later as Donald was on target with his fifth penalty. Back came Evans from 45 metres and it was 15-15.
Harlequins failed to deal with the restart, however, and Bath surged to the line. Three times they tried to ground the ball and Banahan appeared to be closest to scoring only for the TV match official to deny him. It was at least a penalty advantage and Donald was on target again.
It was Bath's turn to set nerves jangling from the restart as both Michael Claassens and Donald had clearance kicks charged down - Easter just failing to make the touchdown.
Donald just kept his cool, lining up another kick at the other end to put Bath 21-15 ahead only for Evans to land his sixth penalty with four minutes left. Harlequins threatened again but a crucial turnover by Guy Mercer won back possession and four vital points.
Saracens missed the chance to go top of the Aviva Premiership as they were deservedly beaten 12-3 by a pumped-up Worcester in a poor match at Sixways.
The visitors could have pulled off an unmerited win if Nils Mordt and Sam Stanley had not missed with four routine penalties.
In a game of stout defence, neither side showed enough attacking nous to threaten the try line but the home pack were the dominant force, which enabled Andy Goode to kick them to victory with three penalties and a drop goal.
Saracens were minus at least eight of their first choice line-out due mainly to international commitments. In contrast, Worcester were only without Samoan captain David Lemi.
The Warriors had the better of the first 10 minutes and were rewarded with the first score when Goode kicked a 30-metre penalty.
Moments later, the visitors had their first chance for points but Mordt was off target with his 45m penalty attempt.
Worcester suffered a blow when young centre Joe Carlisle hobbled off in the 14th minute, to be replaced by Alex Grove.
The Warriors suffered another setback when Mordt brought the scores level with a simple penalty.
Then at a ruck 45m out, Saracens were penalised but Goode could not take advantage and the score remained at 3-3 at the end of the first quarter.
Worcester were denied the first try of the game when, close to the Saracens line, Errie Claassens somehow failed to gather a clever chip ahead from Goode.
However, the hosts were not to be denied points for long as Goode put them back in front with his second penalty.
The outside half then missed a 35m drop goal attempt before Saracens lost flanker Jackson Wray to a leg injury.
A poor clearance from Goode allowed Ben Ransom and Duncan Taylor to counter-attack and when the Warriors were penalised for offside, Mordt had a good chance to tie the scores - but his 35m kick was a poor one.
Worcester extended their lead when a Ransom kick was charged down to put his side under pressure.
Warriors won a ruck close to the visitors' line and Goode fired over a drop goal from point blank range, before the outside half added a penalty to give Worcester a deserved 12-3 interval lead.
The first 10 minutes of the second half represented the best period of the match for Saracens. The visitors dominated in terms of possession and territory but they were not able to convert it into points as James Percival and Josh Matavesi both stole crucial ball from them at vital stages to relieve the pressure.
After 51 minutes, Mordt was presented with another penalty chance but once again he failed as his 30m kick rebounded back off a post.
It could have been worse for Saracens but Goode failed with both a drop goal and a long-range penalty.
It therefore remained at 12-3 going into the final quarter and just afterwards the unhappy Mordt was withdrawn.
Sam Stanley was his replacement but he fared no better on the kicking front, with a 30m penalty miss depriving his side of a bonus point.