Iain Robertson whacked a six down the ground from the bowling of Tim Southee to seal victory with seven balls to spare, but the game almost slipped away.
The Volts needed 30 runs to win from six overs with six wickets in hand. Had they lost from that position an inquiry would have been required. The wicket of talisman Ryan ten Doeschate (29) triggered a panicked collapse. Derek de Boorder (4) played a rash shot, Michael Bracewell (26) holed out after having played nicely and Mark Craig (0) attempted a suicidal single and was promptly run out.
Batting hiccups aside, Otago bowled with much improved discipline and reversed the nine-run loss to the same opponent in Dunedin on Saturday night.
Northern captain Daniel Flynn played pretty much a lone hand, whacking 79 from 53 deliveries to guide his side through to 151 for eight.
Brad Wilson (14), Daniel Vettori (16) and Jonathan Boult (12) were the only other batsmen to get into double figures.
What appeared a middling total was, in the end, quite competitive.
Otago seamer James McMillan bounced back from conceding 14 runs in his first over to finish with two for 24.
Neil Wagner initially struggled with his line too but benefited from a late flurry of wickets, taking four for 33, including the prized scalp of Flynn. They all count but, aside from a beautiful yorker to dismiss Southee, there was element of luck about his wickets.
Nick Beard, who missed Otago's opening three twenty20 matches with a muscle strain, was the standout and finished with one for 18.
He bowled BJ Watling when the batsman tried to hoick a straight delivery over midwicket. At 46 for three, Northern's struggles were compounded when Scott Styris limped off with a suspected Achilles injury.
Jesse Ryder got Otago's chase off to an entertaining beginning, smashing New Zealand's best bowler, Southee, for three sixes and a four in an over. They were all shovelled legside and Southee was none to impressed, using the opportunity to perhaps offer Ryder some batting advice.
Fellow Black Cap Trent Boult rather ruined what was shaping as a good watch. He bent his back and fizzed a bumper almost passed Ryder's bat. Almost. Ryder got a faint edge trying to swat it to midwicket. Still, his 28 from 12 deliveries was more like the Ryder we have come to expect and put Otago on the fast track to victory.
But when fellow opener Sam Wells (16) holed out, Northern sensed Otago was vulnerable and opted for a slip in the hope of picking up the key wicket of ten Doeschate.
Trent Boult had bowled superbly and finished with two for 17. While he could not strike again, Ben Laughlin could.
Aaron Redmond had temporarily relieved the pressure when he went down on one knee and slogged a delivery from Vettori into the big screen. But he was undone by a fabulous yorker from Laughlin which drifted in late and found the base of the stumps.
Bracewell did a fine job supporting ten Doeschate and the pair had the match under control.
But Southee (one for 53) struck with the last ball of his third over, nicking out ten Doeschate and some madness followed. Robertson (21 not out) was dropped with the scores tied but two wonderful strikes down the ground meant that inquiry could be called off.
