Robbie Muirhead's injury-time winner gave Morton the advantage over hosts Airdrie in the first leg of the Championship play-off final.
In the fourth minute of eight added on, and in front of several hundred home fans due to a relaxation in Covid restrictions, the striker rose six yards out to head in a Brian McLean cross from the left following a short corner for a narrow 1-0 win.
It could have been worse for the Lanarkshire side had keeper Max Currie not thwarted Reece Lyon moments later following a swift break.
Lyon had fired a shot against the post in the 79th minute as Morton, who had the best of the second half, pressed for the opener.
League One Airdrie, who had lost just once in 11 games going into the match, might have scored on the hour mark when Jack McKay drove wide from close range.
The return game is at Cappielow on Friday night and Gus MacPherson's side will fancy themselves to finish the job.