Chris Rushworth claimed an early scalp with the first delivery of the second over which saw the dangerman Chaminder Vaas trapped lbw leaving Northants 2-1 after 1.1 overs.
Graham Onions struck the following over with Alex Wakely walking after he nicked the ball to Phil Mustard behind the stumps with the hosts total on 7.
Paul Collingwood made an impact in the 10th over, with Stephen Peters (12) run out thanks to a cracking piece of fielding from David Miller, who timed his throw to the keeper perfectly to see the batsman dismissed for just 12.
David Sales was then caught by Dale Benkenstein at extra cover having faced just two balls with Northants reduced to 41-4.
The Steelbacks were five down after Rob White was trapped lbw by the first delivery of Collingwood’s second over for 21.
Northants skipper Andrew Hall was out lbw to Rushworth in the penultimate over and the hosts lost a further three wickets in the final over, bowled by Mitchell Claydon, with Johan Botha (36) caught at long on by Miller, David Willey (1) bowled two deliveries later and James Middlebrook run out off the final delivery.
Northants posted 124-9 in their 20 overs which included six penalty runs in lieu of the Dynamos slow over rate.
The Dynamos started conservatively and bode their time waiting until the third over to explode into action with Mustard hitting three confident boundaries and Muchall smashing a huge maximum to take the total to 33-0, requiring 92 from the remaining overs to claim the win.
The opening pair batted fluently added a rapid sixty before Muchall was caught at deep square leg by Brooks off Willey for 19.
Mustard went on to hit his fifty from 38 balls, which included nine fours and a maximum in the 13th over with the Dynamos requiring 34 runs.
A few dropped catches saw a few missed opportunities for Northants but the attack didn’t really trouble the pair at the crease who knocked off the final runs required with almost four overs to spare, Mustard 61* and Blackwell 41*.
The Dynamos won by nine wickets, claiming two points.
Durhamccc.co.uk caught up with Man of the Match, Phil Mustard, at the close of play, “I think the bowlers came out and set the tone, they bowled really well and Colly came in and did a job and put them under pressure.
“It’s always nice when Blackie gets in too, he’s good to bat with, you get to stand at one end while he hits fours and sixes! That’s the beauty about Durham, we’ve got people down the order who can hit well and it takes off a bit of the pressure.
“I think when we got to Finals Day a few years ago I think that experience opened our eyes and we should have gone on and done better, we’ve not had the same kind of run in the competition since then but I think this year could be different”.
Durham Dynamos face Derbyshire Falcons at County Ground, Derby on Friday, 7pm start – you can follow the action online as it happens at www.durhamccc.co.uk/live-match-chat
The Dynamos next play at Emirates Durham ICG on Sunday 12 June, 2.30pm start, when Derbyshire Falcons visit to play the return fixture. Tickets can be purchased in advance with the Box Office on 0844 499 4466 priced at £13 for adults and £5 for juniors. Ticket prices on the day are £17.50 for adults and £6 for juniors.