Black Caps and Otago left-armer Neil Wagner showed his class with a six-wicket haul, only for Northern Districts to regain some lost ground.
Wagner took six for 39 to help dismiss Northern Districts for a paltry 132. Earlier, Michael Bracewell had swatted a few final boundaries to help his side reach 326.
Otago opted to enforce the follow-on and at stumps on day two Northern had reached 117 for one.
The visitors still trail by 77 but their position has strengthened.
The day, though, belonged to Wagner.
He exercised precise control over the red ball.
And on a University Oval pitch that was still offering the bowlers some assistance, he was irresistible.
It was his 16th first-class five-wicket bag and his 10th for Otago.
He has now taken 197 wickets for the province.
Only eight players have taken 200 or more wickets for Otago.
Earlier, the Volts resumed on 305 for eight and it was immediately obvious the strategy was to pile on as many runs as quickly as possible.
Bracewell, who had been so watchful the previous day, launched an unbridled attack. Northern responded by dispatching just about everybody to the boundary.
Bracewell got hold of a couple and advanced his overnight score from 135 to 154 before he inevitably holed out. Nick Beard (6) nicked out the very next ball.
It seemed like an unnecessary and hasty end to the innings but it mattered not with Otago striking early and often.
Former Black Cap Daniel Flynn (1) chased a wide, full delivery from Wagner and got the expected edge.
It was way too early in his innings for such an expansive drive.
Brad Wilson might have felt hard done by.
He was trapped lbw but there was a hint it might have been bouncing over leg stump.
Joe Carter followed in the next over.
This time it was the veteran Bradley Scott finding the edge.
Neil Broom took a sharp catch low to his left.
Northern had slumped to 11 for three.
Test hero BJ Watling and Bharat Popli held out for longer than the previous three batsmen.
But Wagner was getting into a fabulous rhythm. Popli needed a life on 14.
Fourth slip Jimmy Neesham could not grab the chance but Wagner moved on from that disappointment by nicking out danger man Watling.
The diminutive wicketkeeper-batsman combined in a world-record sixth-wicket partnership of 352 with Brendon McCullum in the second test against India earlier this month but could not repeat those heroics.
Wagner had three in short order and his fourth, fifth and sixth came just as quickly.
Popli and Scott Kuggeleijn perished in consecutive balls. Kuggeleijn got a terrific delivery.
It swung back and struck the batsman in front.
Ish Sodhi survived the hat-trick ball but not the over.
His middle stump went cartwheeling after Wagner swung it past Sodhi's swinging bat.
Mitchell Santner (51 not out) and Graeme Aldridge (20) provided some much-needed resistance, adding 68 for the eight-wicket.
It formed the bulk of Northern's meagre first innings.
The Volts had bowled just 43.4 overs so the decision to enforce the follow-on seemed easy enough.
However, with Neesham off the park with a shoulder complaint, and Scott needing a spell, Ryder had to partner Wagner with new ball.
Scott relieved Wagner after four overs and secured the only breakthrough, nicking out Wilson.
It took a brilliant diving effort from keeper Derek de Boorder to complete the dismissal.
Northern showed more resolve in its second innings. No-one else was getting out twice in one day.
Flynn (37) and Carter (67) will resume hoping to add to their 105-run partnership.
