The men in Black, Green and Gold led 10-7 at the interval after a nip-and-tuck opening 40 minutes; Freeman’s first try, plus a conversion and penalty from Smith, allowed Saints to come from behind after an early Ruben Van Heerden score.
After the young fly-half had added two more penalties to his tally, Chiefs hit back with Joe Simmonds twice crossing the whitewash to send his side ahead, but another three-pointer from Smith levelled the scores before Freeman’s decisive try on 71 minutes.
After a lengthy early kick battle, Exeter carved out the first opportunity of the game with a scrum penalty which they sent into the corner. After winning the lineout and making several attempts from short range, eventually Van Heerden burrowed over and Joe Simmonds added the extras.
But with 16 minutes on the clock, Smith cut the deficit to 7-3 with a sweetly-struck penalty from 46 metres.
Northampton saw a try ruled out by the TMO after 19 minutes after a move full of skill; Fraser Dingwall’s grubber was picked up by Ollie Sleightholme, but Jack Maunder’s covering tackle forced a knock-on from the wing before Dingwall could finish off the resulting loose ball.
Sam Graham won an important turnover penalty shortly after with Saints pinned inside their own 22, and the men in Black, Green and Gold then took the lead nine minutes from half-time.
It was quick thinking from Freeman to quickly tap a penalty after an illegal clearout on Sleightholme from Olly Woodburn, and the fullback scurried over the whitewash with Chiefs’ defence still retreating.
Smith’s conversion from out wide sailed through the posts again to take the scoreline to 10-7, but there was a blow for Saints in the aftermath as they lost Sleightholme to an HIA from which he did not return.
Northampton extended their advantage shortly after the break as Mike Haywood broke into the 22 and Chiefs were penalised for a deliberate knock-on – Smith kicked the routine three points from in front of the posts to make it 13-7.
The hosts began to unload their bench as Alex Mitchell, Alex Waller and Paul Hill all entered the action, but not before props Emmanuel Iyogun and Ehren Painter combined to win one final scrum penalty which allowed Smith to slot another three points.
However, Saints faced ten minutes with a man down when Aaron Hinkley saw yellow on 53 minutes after he made contact with the head of Maunder following a kick chase.
Chiefs made their numbers count as they stole a Northampton lineout deep inside the hosts’ territory, and having built the phases it was Alec Hepburn who made a punch through the line before Simmonds finished off the try.
Simmonds was off target with the conversion, leaving Saints’ lead at four points, but the fly-half was over again moments later as Dingwall’s kick was charged down and he gathered the loose ball and raced for the line.
This time Simmonds landed the extras, leaving the scoreline at 19-16, however less than a minute later the hosts were level as Freeman charged down a clearance and got over the ball to win a penalty – and Smith once again was unerring from the tee.
With nine minutes to play, Freeman crossed for the game’s decisive score as a penalty was sent into the corner and, after Moon claimed the lineout, the drive rumbled forward before Mitchell stripped the ball off the back and fed the England international to score in the corner.
Smith once again nailed the touchline conversion – his 12th consecutive kick from the tee in Black, Green and Gold. Saints were able to manage the remaining minutes of the game well, before Lukhan Salakaia-Loto claimed a high ball with the clock in the red and Mitchell sent it into touch to confirm the win.
Next up for Northampton is a trip down the M1 to face Saracens in North London next Sunday.
SAINTS: Freeman, Skosan, Dingwall (c), Hutchinson, O Sleightholme, F Smith, James; Iyogun, Haywood, Painter, Salakaia-Loto, Moon, Scott-Young, Hinkley, Graham.
Replacements: R Smith, A Waller, Hill, Nansen, Sylvester, Mitchell, Furbank, Proctor.
CHIEFS: Hodge, John, O’Loughlin, Whitten, Woodburn, Simmonds, Maunder; Sio, Yeandle (c), Williams, Dunne, Van Heerden, Ewers, Pearson, Vermeulen.
Replacements: Innard, Hepburn, Iosefa-Scott, Jenkins, Tuima, Maunder, Becconsall, O’Brien.