Story highlights The string of generosity, bolstered by restaurant staff, lasted 3 1/2 hours

"It's a great feeling to know that there's a lot of great people out there still," a driver said

(CNN) One simple act of kindness can spark a chain reaction of charity -- and a McDonald's drive-thru in Indiana proved it on Father's Day.

It started when a woman in downstate Scottsburg noticed a dad with small kids in the car behind her as she paid at the cashier's window, Tammi Hammonn, a manager at the McDonald's, told CNN.

"She looked back and saw a father with four little kids, with a couple of Happy Meals and such," Hammonn said. "She said she was going to pay for him, and to tell him Happy Father's Day."

But that was just the beginning. From 8:30 p.m. to midnight, every driver paid it forward.

"It was pouring rain, and I was in the middle of it, wondering why my drive-thru was so slow," said Hammonn, who also was a customer -- guest 105 -- that night in the drive-thru lane. "I saw the man in front of me talking to the cashier out in the rain, and I was wondering what was going on."

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