With the circuit moving from the opening rounds in Sweden and Finland to Canada, Randall was victorious in the first race, a sprint, over Norwegian Falla and Ida Ingemarsdotter in Quebec.
However with another sprint scheduled in the middle of three events in Canmore, Falla had the perfect opportunity to get her own back on the American which she did to perfection.
Randall attempted to break the field on the climb but she could not shrug off Falla who stalked her all the way before showing greater speed on the final straight to take the win.
Falla clocked a winning time of 2:57.6minutes, 0.6 ahead of Randall, for her first win of the season and the second victory of her career while Norwegian teammate Celine Brun-Lie was third.
And Falla, who was one of three Norwegians in the final, Ingvild Flugstad Oestberg finishing fifth, admitted it was her plan to sit on the shoulder of Randall before attacking.
"I had to fight really hard to stay behind her [Randall] back. She was going so fast that I knew it was going to break up and I am very happy. I felt better and better during the day," said Falla.
"There is an amazing team spirit for Norway with three of us in the final and two on the podium. It is very friendly and I knew I had an advantage if I stayed behind Kikkan.
"She is very fast and to be faster than her makes me very happy."
Meanwhile in the men's race, Emil Joensson lauded his tactics after powering home on the final straight to pick up his second successive sprint victory on Canadian soil.
Joensson beat teammate Teodor Peterson to the win in Quebec last weekend and this time had Anders Gloersen trailing him in second and Nikita Kriukov in third with a time of 2:33.6.
And Joensson admitted not leading during the early stages of the race, like Italian Federico Pellegrino did before dropping to sixth, helped him claim the win.
"Looking at the heats, most of the winners came from behind to get the speed going into the final straight," said Joensson.
"I didn't want to be first going down the hill, I wanted to be second or third to get the speed and my tactics worked.
"I want to keep competing but we can relax the body over Christmas because it has been a tough start to the season."