The Viewpark team – who had won a penalty shootout at Dundee Violet in the first round after a 2-2 draw – started as underdogs at the weekend at home to Ayrshire cracks Whitletts Victoria.
Although Jack McClair gave Thorniewood an early lead, match favourites Whitletts then scored twice to go 2-1 ahead.
But ’Wood fought back and Darren Bowie netted an equaliser before the hosts produced a beautiful move in the final minute which culminated in Nick Mullen shooting home a dramatic late winner.
“It was a hard fought game,” Thorniewood secretary Eddie Lynas told the Times and Speaker.
"We are getting used to scoring in the last minute. That’s twice it’s happened recently as it was the same when we beat Renfrew 4-3 in a recent league game.
"It’s no mean achievement for us to knock out a team from the league above.
"The secretary of Whitletts came up to me and said: ‘On your second half display you thoroughly deserved it’.
"He said we steamrollered them.
"We want a decent run in the cup because it puts the treasurer in a good mood.”
If Thorniewood are to continue their cup run for at least another round, they will need to get past Conference A leaders Shotts, whom they landed in Monday’s draw.
Thorniewood – co-managed by Jamie Nesbitt and Chris Dolan – will be back in league action this Saturday when they host Dalry Thistle in a Conference B clash which kicks off at 2pm.
’Wood – currently fifth with 23 points from 13 games – will start as favourites against the league's third bottom team but Lynas isn’t taking them lightly.
"The first game of the season we went down to Ardeer Thistle who were relatively known as the whipping boys last season, but we got a surprise because they’ve got a good side this year.
"They beat us 1-0 with a goal in the last minute, so we won’t take any team for granted. We will give Dalry the respect they deserve.”