Northamptonshire moved top of the Midlands/Wales/West Group after clinching a narrow 10-run victory over Somerset at Wantage Road on Wednesday night.
The rejuvenated Steelbacks continued their impressive season with a fifth win in six matches and heaped more pressure on struggling Somerset after defending just 150-8 in front of their home fans.
Somerset, who have reached Finals Day in each of the last four years, have work to do if they are to maintain their fine record in the competition and have now lost three of their opening five group fixtures.
The Cidermen made a dream start to the match when, after losing the toss, Pakistani pace bowler Yasir Arafat removed dangerous Northants duo Richard Levi and Cameron White in the first over of the match.
Arafat became the leading wicket-taker in the domestic T20 competition when he pinned Levi lbw and then had White caught in the deep.
Somerset remained on top and it wasn't until all-rounder Steven Crook came out to bat that Northants gave themselves hope.
The in-form right-hander cleared the boundary four times during his entertaining innings of 63 from just 36 balls and ensured Northants reached a competitive total.
In reply, Somerset openers Marcus Trescothick (22) and Craig Kieswetter put the visitors ahead of the rate with a breezy 38-run partnership inside five overs before Crook continued his inspirational evening with the breakthrough wicket of Trescothick.
The Northamptonshire fightback continued the following over when pace bowler Muhammad Azharullah removed Peter Trego and Nick Compton without scoring.
Kieswetter (38) and Jos Buttler (37) kept Somerset in contention and the latter appeared to be taking the men from the West Country over the line before he was run out in the penultimate over following a mix-up with Arafat.
That wicket signalled the end of Somerset's hopes and Azharullah made Alfonso Thomas his third wicket at the death to end with 3-16 from his four overs.