North Otago secured a valuable bonus point on a day when the ball just did not bounce its way.
Thames Valley scored all of its 26 points during a 20-minute burst.
The home team scored two tries in the final 10 minutes of the half to lead 12-7 at the break in Whitianga on Saturday afternoon.
The Swamp Foxes quickly added two more and led 26-7.
North Otago rallied with tries to hooker Hayden Tisdall and lock Ratu Logavatu.
The Old Golds had an opportunity to clinch victory late in the game, but a rash decision to take a quick tap ended in a turnover and the chance went begging.
Despite the loss, coach Jason Forrest was upbeat about his side’s effort.
And the bonus point secured for a narrow loss may come in very handy as it chases a spot in the top four.
"It just came down to a couple bounces of the ball, to be fair," Forrest said.
"They got a couple of opportunist tries. The one before halftime might have been 40 or 50m and came from our turnover.
"And then the same thing happened in the second half.
"But the pleasing thing to come out of it was we showed some real ticker and, if we could have gone another couple of extra minutes, we possibly could have won it."
North Otago won a late penalty. Instead of kicking for touch and setting up a lineout drive, "one of the boys got a bit eager and quick tapped it".
"That’s footy."
Old Golds centre Hayden Todd produced another strong performance, while lock Ratu Logavatu was outstanding in the lineout.
North Otago moved to 18 points with the bonus-point loss.
It is in fifth place but shares the same points as Mid Canterbury, which edged out Horowhenua Kapiti 15-13.
Thames Valley (25 points) consolidated third spot.
Whanganui (26) destroyed Buller 83-7 and is in second place, while unbeaten South Canterbury (29) cruised to an easy 60-7 win over Poverty Bay.
North Otago and Mid Canterbury shape as the two teams battling for the fourth Meads Cup playoff spot.
The Old Golds have an easier draw. They host West Coast on Saturday, and complete the round robin with an away fixture against King Country.
Mid Canterbury has to play the top two teams.
In the other Heartland Championship games, King Country beat East Coast 32-21 and Wairarapa-Bush beat West Coast 42-30.
Heartland Championship
The scores
Thames Valley 26
Sam McCahon 2, Tayne Tupaea, Cameron Dromgool tries; Todd Doolan 3 con
North Otago 21
Ben McCarthy, Hayden Tisdall, Ratu Logavatu tries; McCarthy 3 con
Halftime: Thames Valley 12-7.
