Ashton Agar and Steven Finn took three wickets apiece as Middlesex staged an astonishing comeback to beat Hampshire by 22 runs at Lord's in the Vitality Blast.
Hampshire appeared to be coasting at 89 for one, chasing a modest target of 166 for victory, but they somehow contrived to throw away their last nine wickets for just 54 runs.
That turnaround secured Middlesex's first victory in the tournament for five games and lifted them off the bottom of the South Group table.
Fidel Edwards (two for 30) and spin duo Mujeeb Ur Rahman and Liam Dawson ensured that Hampshire restricted their hosts to 165 for eight after winning the toss, despite Paul Stirling's accomplished half-century.
Max Holden (22) kept Stirling company throughout the powerplay, but their stand of 58 was broken when the left-hander called a single that never looked on and was comfortably run out by Edwards' throw.
Stand-in captain Eoin Morgan's promotion to three in the order failed to pay off as he made just two before holing out to deep midwicket - and Middlesex's innings never gained any kind of traction.
That was no reflection on Stirling, whose knock of 60 from 44 balls included five fours and three sixes before he eventually perished driving Colin Munro to long-on.
Dwayne Bravo hammered a rapid 20 but, once he was run out attempting a risky single, Middlesex's hopes of a par score evaporated and only some spirited late blows from Tom Helm hauled them up to 165.
That target looked unlikely to cause Hampshire problems, although James Vince surrendered his wicket in the first over by spearing an attempted pull back to Finn (three for 21).
But Munro was soon into his stride with some clean hitting, dispatching all the Middlesex seamers to the boundary with regularity as he rattled up 58 from 29 deliveries.
The New Zealander shared a second-wicket partnership of 85 with Sam Northeast (27) before the latter charged Agar (three for 17) and missed, allowing John Simpson to whip off the bails.
Agar then gave his side a glimmer of hope with two wickets in as many balls as Munro heaved one to long-on and Rilee Rossouw scooped the next into the hands of Stirling.
Hampshire's wobble soon turned into a full-scale collapse as Finn followed Agar by removing Chris Wood and Tom Alsop with successive deliveries.
And it was Agar who applied the finishing touch in the penultimate over, calmly taking a catch at long-on to dismiss last man Edwards off Bravo.