A gesture by a customer at Heav'nly Donuts in Amesbury, Massachusetts triggered a chain reaction on Saturday that led to a lot of smiles.

The staff began counting at around the seventh car as the driver paid for the order of the customer behind them, after getting theirs free.

"It was the best twelve dollars I ever spent," said the unemployed woman who took the free drinks but then started the chain as the second in line.

It only ended when there were no more people in line whose orders could be paid for.

The phenomenon of paying for the person behind you in line at a drive-thru window goes back at least five years. In 2008, KUSA in Colorado reported on it in this video for CNN.

And, it isn't happening only in the U.S. One pay-It-forward chain lasted for three hours at a Canadian coffee shop in Winnipeg over the winter holiday last year.

(READ the story at WBZ-Boston)