It may sound like this is the plot of a spy novel, but "The Bus of the Shetlands" is a real covert operation aimed at the resistance of Nazi-occupied Norway during World War II.

In the depths of winter and under the cover of darkness, a convoy of small fishing boats left the security of Scotland's northernmost islands, delivering valuable cargo and special agents to bays and fishing ports 200 miles away from the Norwegian coast.

During the dangerous journey back, refugees fleeing from the occupation were hidden in fishing boats as they sought shelter in the British Isles.

To commemorate the 80th anniversary of the victory of Europe (VE), six historic vessels that form part of the Shetland bus fleet will set sail again from Bergen, Norway to replicate their journey back to the Shetland Islands.

They plan to arrive at Lerwick in time on Tuesday for the anniversary.

Norway was invaded by Nazi Germany on April 8, 1940, a few months before France's entire occupation.

The Norwegian government and its royal family, including King Hacon VIII, were forced to exile in London, and thousands of Norwegians followed fishing boats and other small boats across the North Sea to seek asylum in Britain.

In July 1940, British Prime Minister Winston Churchill formed a secret organization called the Director of Special Operations (SOE), whose sole purpose was to conduct espionage and sabotage missions in Europe.

The convoys of Shetland are part of the Norwegian branch of the state-owned enterprise, supporting Norwegian resistance.

Between 1940 and 1945, they conducted 200 crossings in the North Sea, transported hundreds of resistance athletes, tons of weapons and supplies, and rescued more than 300 Norwegian refugees from fleeing the occupation.

The 200-mile crossing is conducted in winter to make the most of the dark time and avoid being discovered by German patrols.

But this means that the sea is often dangerous.

The crew and passengers on board not only have to endure not only the heavy conditions in the North Sea, but also the ongoing risks found by German aircraft or patrol boats.

On September 27, 1941, MK Arnefjord left the island of Hernar and arrived in the northwest of Bergen, carrying 20 refugees.

Even though the weather began to calm, they soon encountered a violent storm. Everyone on the boat was seasick and some discussed looking back.

Eventually, Arnefjord crossed it safely and delivered the crew and passengers to Mousa Island in the Shetland Islands.

But others are not lucky. That weekend, out of the six ships crossing the North Sea with Anev County, there were only four.

A total of 10 fishing boats were lost in the convoy of Shetland and 44 soldiers were killed.

Morten Neset, the current captain of MK Arnefjord, will return to Shetland as part of the VE Day commemoration.

He told the BBC Scottish News that the ships must be transited in winter or late autumn to avoid being discovered by the Germans.

"If they crossed on a clear summer day, they would be found immediately," he said.

“The buses in the Shetland Islands are very important to the general population of Norway because it shows that there are people 'supporting them' in resisting the occupation."

Bill Moore of the Shetland Bus Friendship Association said that while it is difficult to say what it has had to do with the war, it is an important part of the resistance movement, which brings optimism and hope to the people of Norway.

People say they are "taking the Shetland bus" as code to escape careers.

The Shetland residents hosted Norwegian soldiers and refugees throughout the war, forming a lasting bond between the two sites until today.

The Liberation Convoy will leave Bergen, Norway, at 19:00 on Sunday and plans to arrive at Lerwick on Tuesday, May 6.