The Double-A Rock Cats entered the ninth trailing, 4-1, and having collected just a pair of singles to that point.
Thunder closer Ryan Flannery got the final out of the eighth, but permitted a walk and a single then hit a batter to start the ninth. Flannery fanned the next hitter -- Chris Hermann -- but it would be the last out he'd record.
Flannery walked James Beresford and Twins' No. 2 prospect Aaron Hicks to force in two runs. That brought Arcia to the plate and he lined a single to right that scored Estarlin De Los Santos and Beresford.
Before the bullpen gave away the lead, Hall cruised through his six innings, scattering a pair of hits and three walks. He seemed poised for his seventh win of the season for the Yankees' affiliate, particularly after Trenton scored three in the fifth.
With two outs in that frame, singles by Addison Maruszak and Jeffrey Farnham, and an RBI double by Damon Sublett knocked New Britain starter Blake Martin out of the game. Eastern League stolen-base leader and Eastern Division All-Star Abraham Almonte singled in Farnham and Sublett to give Trenton a 3-0 lead.
Another Almonte hit -- this time an RBI double -- gave Trenton a 4-0 advantage in the seventh.
Hall, who lowered his ERA to 3.97 with the six scoreless innings, gave way to the Thunder bullpen, which permitted just an unearned run in its first two innings before the ninth-inning meltdown.
Arcia, the Twins' No. 4 prospect, was the hero in his 10th Double-A game after spending most of the season with Class A Advanced Fort Myers. He's now hit safely in eight of his nine games.
The win brings New Britain to within two games of Trenton and Reading, who are tied for first in the Eastern League Eastern Division.