Bath took over at the top of the Guinness Premiership thanks to two tries from their South African scrum-half, Michael Claassens.
The bustling former Springbok No 9 earned the plaudits of Jim Mallinder, Northampton's director of rugby, and also from Bath's head coach, Steve Meehan, who said: "Claassens is like an extra back-row forward. And he would have wanted to play well today because his parents have come over and were watching."
Watching was just what Saints were not doing when the 5ft 10in half-back propelled his 14st frame over from a close-range scrum late in the second half, after dummying to Joe Maddock out on the blind-side wing. His fly-half, Butch James, converted the scrum-half's second try.
That settled the result and although Saints hit back with a late try through the lock Juandre Kruger, they were too far behind.
Bath had got off to a fizzing start when, with just a minute and 15 seconds on the clock, James collected the ball from a scrum and slid a grubber kick through the Northampton defence.
Bath's bulky but surprisingly nimble left wing, Matt Banahan, chased after it and managed to touch down. James converted.
It was Banahan's second try in two minutes of play, the previous one having come in the dying seconds of last week's match here, but Bath then fizzled out somewhat as Saints came back at them. Penalties were exchanged between James and his opposite number, Stephen Myler, before Bath had a chance to increase their lead on the stroke of half-time.
Sadly, they handed the ball to Jack Cuthbert for a 50-metre shot. Bath's other big wing, playing at full-back here, may have a big boot but on this occasion he got his foot right under the ball and ended up chipping it as if he was using a nine iron.
The miss kept Northampton in touch, their points coming from two penalties kicked by Myler. They could have had more but the bounce of the ball and luck in general did not go their way. Some of the high balls they put up were badly misjudged by Cuthbert, but the ball just never seemed to fall kindly for the Saints. Nor, for that matter, did some of the decisions of the referee, Andrew Small.
After the break, and after Myler had edged Saints closer with his third penalty, Bruce Reihana failed to gather a through ball cleanly and ended up sending it deeper into the Northampton 22 with his knee. A scrum was awarded to Bath for an apparent knock-on. Four minutes later, after sustained pressure from the home team, Claassens barrelled over from close range for his first and Bath's second try.
Bath: J Cuthbert; J Maddock, A Crockett, S Hape (E Fuimaono-Sapolu, 62), M Banahan (A Higgins, 64); B James, M Claassens; D Flatman, L Mears (P Dixon, 69), M Stevens (D Bell, 78), S Hooper (J Harrison, 69), P Short, A Beattie, J Faamatuainu (D Browne, 62), M Lipman (capt).
Northampton: B Reihana (capt); P Diggin, J Clarke, J Downey (C Spencer, 72), S Lamont; S Myler, L Dickson (B Foden, 56); S Tonga'uiha (T Smith, 67), D Hartley, E Murray, I Fernandez-Lobbe (C Day, 67), J Kruger, M Easter (M Hopley, 72), R Wilson, S Gray.
Referee: A Small (Bedfordshire).