Berwick Rangers scored a last-minute equaliser, but Declan McManus then fired an extra-time hat-trick to send Morton through in a thrilling Petrofac Training Cup tie.
The talented striker, on loan from Aberdeen, scored in 105, 114 and 117 minutes to kill off Berwick’s challenge after Lee Currie’s last-minute equaliser at the end of normal time had threatened to cause an upset in the second-round tie at Cappielow.
Overall, Colin Cameron’s men can be proud of their efforts against a team one division above them.
With 16 shots on target, there was no shortage of attacking play from the visitors, who had new striker Craig Dargo to thank for taking the game into extra time.
The veteran, whose signing was only announced by the club earlier in the day, came off the bench to make his debut when Berwick were trailing 2-1.
With a minute left he was brought down in the box to earn a penalty.
Currie’s spot kick was well saved, but the captain reacted quickly to convert the rebound and extend what had been an entertaining 90 minutes.
The Greenock side won the League Cup tie against their League Two opponents 2-1 just two weeks ago, and this match was equally close.
Berwick went ahead after just nine minutes when Scott Maxwell fired a 20-yard drive into the net off the underside of the bar.
But Morton were level just five minutes later when Stefan McCluskey’s shot rebounded into the path of his brother Jamie, who poked home from close range.
Spurred on by the goal, the home side pressed for a second.
But it was Berwick who nearly took the lead on the counter attack when a Paul Willis strike hit the post before Morton goalkeeper Nicolas Caraux could gather.
With half time approaching, and Berwick ruing their hard luck, Morton grabbed a goal to give them the perfect lift just before half time.
Thomas O’Ware’s looped header over Berwick goalkeeper Billy Bald made it 2-1 to the homse side at the break.
The second half was fairly even, with Berwick going toe-to-toe with their League One opponents.
Just when Morton thought they had done enough to squeeze through to the quarter-final, there was drama in the last minute.
The referee awarded Berwick a penalty when Dargo was brought down by Morton’s Ricki Lamie.
Although the spot kick was superbly saved by Caraux, Currie reacted quickest to fire home the rebound and take the tie into extra time.
Bald came to Berwick’s rescue when impressive run and cross by Jamie McCluskey found McManus, the goalkeeper pulling off a superb stop.
But with Berwick on the back foot, it looked like a Morton goal was coming and it arrived just before the extra time interval when McManus lashed an unstoppable shot into the top left corner.
Berwick refused to give up, forcing a couple of corners in their search for an equaliser.
But McManus killed off Berwick’s hopes of more late heroics when he ran on to an O’Ware flock on to go round Bald and slip the ball into the gaping net.
At that stage, Berwick just wanted the final whistle to sound. But the attacking line-up Cameron had deployed to force an equaliser in normal time came back to haunt the manager when McManus scored again.
The striker rubbed salt in Berwick wounds by sliding the ball through Bald’s legs to complete his hat-trick.
The home side were reduced to ten men when Jamie McCluskey was shown a second yellow card, this time for diving.
But it was all over as a contest by then.
Morton: Caraux, Miller (Hands 77), Crighton, Milojevic, Lamie, S McCluskey, McKee (Russell 87), Pepper, J McCluskey (Kilday 64), McManus, O’Ware. Subs not used: Scullion, McNeil, Gaston.
Berwick Rangers: Bald, Jacobs (Dargo 79), Fairburn, Hoskins, Maxwell, Willis, Notman, Cameron (Dalziel 87), Gold, L Currie, Lavery (Russell 74). Subs not used: Horribine, Andrews, Bauld, Miller.
Referee: Barry Cook.