A controversial penalty just past the hour mark turned Bath City's evening in Cornwall on its head.
Shane White's spot-kick proved the vital ingredient as Truro built in confidence to claim a win their second half performance perhaps deserved.
Truro almost made the ideal start when inside a minute Isaac Vassell latched on to a long ball over the top, got the better of Andy Gallinagh and shot too close to Steve Phillips.
Soon after, Gary Owers' men, culpable for letting in a number of early goals this season, struck with one of their own.
Danny Greenslade's pass down the left was picked up by the returning Eliot Richards.
He showed more desire to beat Aaron Pugh to the ball before firing it across from the byline to the onrushing Dave Pratt, who headed in from a yard out to give the visitors a seventh-minute lead.
It clearly rattled the home side with Phillips rarely troubled, only notably called upon to gather Ollie Knowles' free-kick.
City's pressing game nullified several attacks, Dan Ball in particular impressing in defence, and they could have nicked a second just before the interval when Richards' shot on the turn was just collected by Martin Rice at the second attempt.
The second half saw Truro forced into a change early on when Aaron Bentley clattered into an advertising hoarding under pressure from Liam Kelly, with Jamie Richards taking his place.
City also introduced Tyler Harvey for his debut, in place of Richards, before the penalty decision on 61 minutes swung the game in the home side's favour.
Vassell chased Connor Riley-Lowe's header forward and, when going wide of goal, went to ground as Phillips dived to palm away the danger.
Referee Hulme decided he had connected with the man first and, amidst several protests, awarded a penalty.
White confidently scored, despite having missed from the spot at Twerton, and in the aftermath the City stopper was booked for petulantly tripping Dan Green during the celebrations.
It looked like a sixth 1-1 draw in eight games for Owers, but instead he was left further frustrated as his side fell behind on 80 minutes.
Chas Hemmings was cautioned for a strong challenge on Knowles on the halfway line. Rice's long free-kick was headed back by Pugh to substitute Les Afful who, despite not getting the desired connection on the shot, had the direction to beat Phillips.
It was the 8,000th goal City had conceded in all competitions since formation and one which soon after earned a ticking off for Owers from referee Hulme for his protests regarding the initial free-kick.
The Romans' only real opening of the second half fell to substitute Harvey. Racing onto Dan Bowman's intelligent through ball, the forward lost his composure and blazed wide with just Rice to beat.
Truro closed the game out brilliantly, penning City back, and added to their tally with a third goal moments before the final whistle.
Knowles' corner was headed out by Gallinagh but collected by Afful on the edge of the box, who this time hit a sweet strike that zipped past Phillips.
The City boss was left enraged at the end by a few decisions, not quite in the same league as the watching outspoken Rotherham boss Neil Warnock, but the City chief will take some consolation from the first half showing and hope his side build on it in a bid to beat the drop.
Truro City: Rice, White, Riley-Lowe, Brett (Afful 58), Bentley (Richards 53), Pugh, Cooke, Knowles, Green, Duff (Jay 71), Vassell. Subs not used: Ash, Dawson.
Bath City: Phillips, Bowman, Greenslade, Gallinagh, Ball, Hemmings, Kington (Simpson 74), Kelly, Murphy, Pratt, Richards (Harvey 54). Subs not used: Williams and Hutchinson.
Referee: Richard Hulme.
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