Nancy and Don Zwaagstra of Bedford, N.S., mistakenly drove into the United States from Stanstead, Que., a town in which several streets straddle the international border. (CBC)

A Nova Scotia couple who took a wrong turn in Stanstead, Que., and mistakenly drove into the United States last weekend is on a crusade to make sure no one else experiences the travel nightmare they went through.

Nancy and Don Zwaagstra's road trip started innocently enough. They had just dropped off their son, who attends a private boarding school in Stanstead, at a hockey tournament and were killing some time before going back to watch the game

"My curiosity got the best of me. I wanted to look at some buildings and architecture," said Don Zwaagstra, of Bedford, on Thursday. "I drove up a street in Stanstead, and at the top of the hill, we took a left hand turn and ended up in the United States."

Stanstead, about 160 kilometres southeast of Montreal, is famous for its elegant homes that sit partly in Canada and partly in the United States. An old opera house that straddles the border even has a line drawn on the floor indicating the international border.

"We were busy admiring the churches, but there was no signage there," Nancy Zwaagstra said.

Unbeknownst to them, they had inadvertently wandered across the international border from Stanstead, Que., into Derby Line, Vt., and before they knew it, they were stopped by U.S. police.

"They told us that we had entered the U.S. illegally, and they had to call border patrol," Nancy Zwaagstra said.

"They called border patrol, and immediately, three or four border patrol trucks came and escorted us [to the customs office]."

The couple was escorted to the official, marked border crossing, which is on the main street that runs north-south through both towns.

The U.S. Customs and Border Protection officers were not sympathetic to the Zwaagstras explanation of how they had innocently crossed the border into the U.S., said Don Zwaagstra.

"They suggested that we could be fined; we could have our vehicle impounded; we could be arrested, deported, a number of things," he said. "You know, a couple of those types of insinuations, and it depended a lot on how our criminal records checked out."

In the end, the Zwaagstra were simply escorted back to Canada — after they were fingerprinted, photographed and forced to sign documents admitting what they had done.

"I couldn't believe it was happening, and I was totally humiliated," Nancy Zwaagstra said. "I was fingerprinted; I had my mug shot taken. It was a terrible feeling."

The Zwaagstras are angry because they say the Canada-U.S. border should be marked everywhere, not just at the official crossing.

They complained to Phillipe Dutil, the mayor of Stanstead, and he has erected a temporary barrier on the street where they strayed into the U.S.

But the couple is now campaigning to have clear border markings in all border towns across the country.

They've sent out a barrage of emails, including to Prime Minister Stephen Harper, asking that the Canadian government make sure that the border is clearly marked.

In February 2009, the Canadian government announced it was going to beef up protection at unmanned crossings at the border in Quebec, and planned to build barriers on secondary roads connecting Stanstead, Que., and Derby Line, Vt.