In an amazing game in the rain at Treyew Road, City were denied a vital victory as their National League South play-off hopes suffered a setback.
And their nemesis was Maidenhead's Dave Tarpey, who scored all four of his side's goals in a thrilling contest which, in the end, Truro were grateful to come out of with a share of the spoils after three times enjoying two goal leads.
It had all looked so good for the home side as they they raced into a 2-0 lead inside the opening 14 minutes, with new Exeter City on loan signing Matty Jay playing a key role on his debut.
The diminiutive 19-year-old first calmly rolled the ball across the area for Dan Green to sidefoot home after eight minutes and then Jay netted himself as he turned and shot past the left hand of Maidenhead keeper Carl Pentney.
City should really have finished the Berkshire side off, but four minutes before half time Tarpey beat the City offside trap and finished calmly past a helpless Martin Rice.
However, in the first minute of stoppage time, Isaac Vassell restored City's two goal advantage, heading home from close range from Ryan Brett's corner.
Maidenhead had the elements in their favour after the break and quickly pulled a goal back when Tarpey put away the rebound after his first effort had hit the post.
But immediately Vassell struck again for City to put them 4-2 up and seemingly on their way to victory as they led by two clear goals for the third time.
However, the visitors continued to push as City got deeper and deeper and 10 minutes from time Tarpey completed his hat-trick from the penalty spot, after City substitute Aaron Dawson had been penalised for a trip in a goalmouth scramble.,
City were hanging on as the conditions deteriorated, but could not hold out and a minute from time Tarpey latched on to Joe Gorman's cross from the left to make it 4-4 with his fourth goal and only a terrific save from Rice denied the visitors a winner.
It meant that City have now lost just once in their last 16 league games and are unbeaten at home in five months, but it still felt like a defeat.
They remain seventh in the table, three points off the play-offs.
CITY: Rice; White, Pugh, Richards, Riley-Lowe; Knowles (Knowles 67); Green, Cooke (Duff 63), Brett, Jay (Afful 73), Vassell
Subs (not used) Gill, Mitchell.
Yellow cards: None
MAIDENHEAD UTD: Pentney; Huggins, Gorman, Upward, Nisbet, Inman, Tarpey, Smith (Wiltshire 63), Reid, Wright (Barratt 60), Mulley
Subs (not used): Olorunfemi, Peters.
Yellow cards: None
Goals: Green (8) 1-0, Jay (14) 2-0, Tarpey (41) 2-1, Vassell (45+1) 3-1, Tarpey (53) 3-2, Vassell (54) 4-2, Tarpey (pen 80) 4-3), Tarpey (89) 4-4.
Referee: Daniel Cook (Hampshire)