Jamie Hislop scored with 47 seconds left to give Calgary its tie in Toronto.
After John Anderson gave the Maple Leafs a 5-4 edge on a disputed goal at 14:32, Hislop picked up Paul Reinhart's centering pass and slid the puck past goalie Mike Palmateer and into the far right corner.
Anderson swatted Peter Ihnacak's rebound into the Calgary crease and it appeared goalie Don Edwards made the save, but referee Ron Wicks ruled Edwards pulled the puck past the goal line. It was Hislop's third goal this year.
Toronto took a 1-0 at 12:26 of the first period when Terry Martin redirected Rick Vaive's power-play drive past Edwards. Lanny McDonald tied the score at 17:21 of that period with his 10th goal in 10 games, deflecting a shot past Palmateer.
Borje Salming scored on a 55-foot power-play shot 40 seconds into the middle period to give the Maple Leafs a 2-1 lead. But Kent Nilsson tied it at 5:01. Bill Derlago's goal midway through the period gave Toronto a brief lead.
Dennis Cyr of Calgary made it 3-3, sweeping a rebound into the unattended net at 14:34 of the second period. Nilsson provided Calgary with a 4-3 lead 24 seconds later and Martin scored at 10:52 of the final period to make it 4-4, slamming a short shot to Edwards' right.