It is not as if Dunfermline had not been warned, but for the second time this season Jai Quitongo proved the match-winner for Morton with a late and dramatic winner.
The 20-year-old had sealed a 3-2 win for the Cappielow men in the league earlier in the season with a decisive injury-time strike and, shaking off a shortness of match-fitness, he repeated those feats again to send his club into the fifth round of the Scottish Cup.
“Jai looked surprised to score? I was a bit surprised as well!” beamed manager Jim Duffy. “We know Jai has got a real talent; he’s strong, he’s quick. But he’s had a stop-start season with niggly injuries.
“He needs a run of games, you could see he was struggling with his fitness. But he’s a talent.
“It’s a fantastic result and a terrific cup tie. It was great to get the win.”
Gary Oliver had earned the visitors the breakthrough in a tie that swung one way and then the other. The former Hearts striker popped up in acres of space on the right side of the area to fire beyond Lee Robinson and into the far corner of the net.
Dunfermline should have equalised moments later when a superb Ryan Williamson run and cutback was skewed wide by Joe Cardle but they restored parity 11 minutes into the second half as Declan McManus blasted a shot through the arms of Derek Gaston.
If the Morton keeper could have done better on that occasion he responded magnificently to repel a bullet header from Nicky Clark shortly after, and Quitongo snatched the victory for the visitors when he curled in a superb winner five minutes from time on the break.
Dunfermline boss Allan Johnston moaned: “I thought when we scored we would go on to win it.”