But Vegas replied once again on their fourth powerplay of the game, Marner setting up Dorofeyev for his 35th of the season to even the score at 3-3 before the second intermission.
Then came the delay.
An ice issue to the left of the Calgary goal prompted a full-on team approach by the T-Mobile Arena ice staff, with the four officials and leaders from both sides keeping a watchful eye on proceedings. But after a 29-minute delay, the ice was deemed useable, and play continued on.
The game remained tied until the 12:20 mark of the frame, when Brett Howden gave Vegas its first lead of the night with a wrist shot from the slot.
Ivan Barbashev added an insurance marker two-and-a-half minutes later before Marner completed his hat-trick with a wraparound goal with 89 seconds left in the game.
In the first period, Flames defenceman Zach Whitecloud was saluted for his eight years of service - and Stanley Cup triumph - with the Golden Knights organization, the video tribute drawing a standing ovation from the 17,912 in attendance.