A century from Wes Durston spurred visitors Derbyshire Falcons to victory over the Steelbacks at the County Ground and elevated them into the top four in Group A of the Royal London One-Day Cup.
Derbyshire prevailed by six runs on the Duckworth-Lewis method, and have three games remaining in the group stage as they pursue a quarter-final place.
Durston's 108 inspired Derbyshire to reach an imposing 211 for six from their 32 overs, and the visitors then bowled with skill and patience to keep the STeelbacks shy of their revised target of 227, with James Middlebrook bowled off the final delivery of the game.
When Wayne Madsen won the toss, Derbyshire batted first but a torrential downpour halted play after just 8.1 overs.
It took the groundsmen just over three hours to get the pitch fit once more for play and, on resumption, Durston's powerful hitting, combined with the experience of Marcus North, saw them put on exactly 100 in just over 13 overs.
It helped that they were facing a weakened Northamptonshire attack that was missing England Lions' David Willey as well as the injured Steven Crook and Olly Stone.
Too many Steelbacks fielders were put under pressure on a greasy outfield, which allowed Derbyshire to set a stiff target for the team who had won just one game in all competitions in the last month.
Mark Footitt quickly removed the home captain Kyle Coetzer for 10, bringing Richard Levi and Adam Rossington together.
The 21-year-old Rossington has made a favourable impression since arriving on loan from Middlesex, but when he skied a Durston long hop to Billy Godleman at square leg, having helped Levi put on 53 for the second wicket, Derbyshire were on top.
Wickets fell at regular intervals and when Levi went for an enterprising 62 off 66 balls, with 73 wanted off seven overs, the dye appeared to be cast.
Andrew Hall and Graeme White kept the hosts keen until a fabulous catch from Godleman in a swirling breeze at mid-wicket removed White.
Hall's boundary through square leg gave the home side some hope to leave 47 wanted off the last four overs.
But Footitt conceded just four runs off the 29th over, leaving the South African too much to do.
When Hall was bowled by Cotton for 43 in the next over, the Steelbacks’ chance had gone.
Despite the penultimate over from Footitt costing 23 runs, Middlebrook could not hit a six from the final delivery that would have secured a tie.