Then the opening bowlers twisted the knife, capturing two quick wickets to put their side firmly on top at stumps on day two.
Otago conceded a first-innings deficit of 74 runs and faced a tricky three-over period at the end of the day.
Had the Volts gone into the sheds with all their second innings wickets intact, that deficit might not have looked so bad.
But Craig Cumming and Aaron Redmond multiplied the misery, adding just two runs between them and leaving Otago four for two at stumps.
Earlier, Northern looked in danger of falling short of Otago's tally of 301 when it slipped to 183 for five.
But all-rounder Joseph Yovich, playing in his 100th first-class match, combined with Anton Devcich and Jono Boult in damaging partnerships worth 121 runs.
The 33-year-old was hunting for his fifth first-class 100 and made a 128 not out in the corresponding game last season.
But on 61, having played nicely, he designed his own demise, pushing the ball into the covers and setting off on a single which never looked on.
Redmond swooped on the ball and Nathan McCullum, who earlier replaced Ian Butler in the playing XI, gathered the throw and completed the dismissal.
Graeme Aldridge proved nuisance value, adding 32 to help the Knights reach 375.
Neil Wagner was easily the best of the Otago bowlers.
He bowled with pace and the left-armer used the angles to his advantage, taking a career-best six for 55 from 24.5 overs.
The South-African born 24-year-old is in his third season with Otago and hopes to qualify for New Zealand.
He was a little inconsistent last season but has made an impressive start to the summer.
With the rest of the Otago attack coming in for some punishment, Wagner kept a tight line and reaped the rewards.
However, it was James McMillan who got the first breakthrough.
Opener Daniel Flynn looked to pick up were he left off.
He had played some delightful shots at the end of day one and added 17 to his overnight score.
But one short of his 13th first-class half century, McMillan sent his off stump cartwheeling after enticing him in to a drive.
Brad Wilson was joined by the experienced Michael Parlane and the pair guided the visitors safely past 150.
Wagner pounced just before lunch.
He bowled Parlane who played positively for 40, and nicked Wilson out for 60.
All-rounder Sam Wells snaffled James Marshall's wicket with a catch off his own bowling just before lunch to help seize the initiative for the Volts.
Scott Styris, who replaced Bradley Scott in the playing XI in the morning offered a catch to Cumming on 15 which left the innings teetering.
But Yovich and Boult added 76 for the seventh wicket.
Wagner eventually got rid of Boult and Aldridge, and removed No 11 Owen Ivins in his debut.
Otago will resume today trailing by by 70 runs with eight second innings wickets in hand.
Auckland faces an uphill struggle against Canterbury in its match in Christchurch, NZPA reports.
After two days, Auckland trails by 285 runs with five wickets in hand after Canterbury reached 435 for nine declared, highlighted by Dean Brownlie's 153 not out.
In response, Auckland was 150 for five.
