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MIAMI (CBSMiami) — He faced a sentence of 15 years behind bars in a Cuban prison. But for American Alan Gross, the cruelest cut was remaining a captive as his mother — a world away — was dying and asking for him.

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It is now a chapter in U.S. history — the man considered by many as a catalyst for change in Cuba-U.S. relations looks back as CBS4 News looks beyond the headlines with Michele Gillen’s exclusive one-on-one.

Here is Part 2 of her ongoing series. Read Part 1 here.

“Around 10 o’clock at night, I hear ‘bang, bang, bang’ at the door. I go up and say who is it? I look through the peephole and there are these four giant guys standing on the other side of the door saying, ‘Open the door,'” recalls Gross.

For Gross, danger had been foreshadowed but the reality of it came crashing down with that knock on his Havana hotel room door.

“I opened the door and they say, ‘Collect your stuff, you are coming with us,'” he said.

His wife Judy was anxiously awaiting his arrival back in Maryland and his expected phone call that he had left Cuba and had arrived home — a call that didn’t come.

“I called the airline. I knew that it was confidential. I knew they couldn’t give me the information but I asked anyway. I must have had a desperate tone and I explained to them what I was fearful of and I said you really need to tell me. So they confirmed he was not on the flight,” said Judy.

Meanwhile, Gross found himself interrogated day after day.

“They accused me of being a CIA agent or a Mossad agent. But it was laughable. And they didn’t pursue it,” reflected Gross, who had a translator present, as he says he did not speak Spanish.

“You went to Cuba and did this work and didn’t speak Spanish,” asked Gillen.

“What spy in his right mind would do that,” Gross sarcastically questioned.

Gross’ arrest led to a 15-year-prison sentence.

What was Alan Gross doing in Cuba and who was he working for? An analysis of funding for the project leads us to the U.S. Agency for International Development (USAID), headquartered in the nation’s capital.

USAID is the federal agency that oversees foreign aid and was the funding agency for the project Gross worked on through a prime contractor. Gross sued both parties.

“I believe the federal government should be liable for its actions no matter where in the world they take place,” said Gross.

“According to one of the lawsuits, you brought up that you had raised concerns about the dangers of the equipment being found,” asked Gillen.

“I was becoming more and more uneasy with each successive trip. I was,” Gross admitted. “It is illegal to distribute anything in Cuba paid for in part or full by the U.S. government.”

“And you did not know that,” Gillen asked.

“No. Absolutely not,” said Gross.

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His confinement continued. At one point, he only cared about finding a way to see his mother in her last days. Fighting cancer, she wanted him by her side. It left his wife “worried about his emotional state.”

“Because he had said to me, I don’t want you to come back,” shared Judy.

Gross and his supporters were willing to do anything for him just to be released for a few days.

“I signed an oath to Raul Castro that I would return. There were people who would trade places with me so I could go and visit my mother and the government of Cuba just did not respond. I have a lot of forgiveness in my heart. That will not be forgiven,” Gross held firmly.

For Gross, the best phone call was the last one placed by his wife. In cryptic words, Judy Gross signaled he was coming home.

“I said, ‘Alan, this is our last phone call together like this,'” shed recalled.

With freedom, he says he holds onto the thought of the journey he wants to take — that is, a return to Cuba.

“You want to go back,” asked Gillen.

“In a heart beat. If for no other reason than the people of Cuba. There is something very symbolic about me going back. I was a catalyst. An unintentional catalyst perhaps. Since I have been released, I am an intentional catalyst. By allowing me to return I think that sends a message out there that there is a new chapter for all of us,” said Gross.

Alan Gross sued the contractor that hired him and that lawsuit resulted in a settlement which is confidential.

He was unsuccessful in suing the federal government.

CBS 4’s investigation into U.S.-funded development projects in Cuba continues.

Below is a statement from USAID responding to a series of questions CBS4 News presented to the agency, including regarding Gross’s work, arrest and lawsuit:

On the project Mr. Gross was working on in Cuba?

“Alan Gross was in Cuba to connect people to the outside world and provide people with better access to information, ranging from access to newspapers to Internet access. USAID’s programs respond to the interests and needs of Cuban groups and individuals. Despite the restrictions placed upon them by their own government, Cuban citizens continue to ask for more support to increase their ability to network and communicate with one another.”

The role of USAID in that project?

“USAID contracted with DAI to provide support to marginalized communities in Cuba. Mr. Gross worked on this project as a sub-contractor of DAI.”

Reaction to the lawsuit that Mr. Gross filed against USAID?

“The lawsuit against USAID was dismissed by a trial court and the subsequent appeal was rejected by the U.S. Supreme Court in April 2015.”

Were any changes made regarding USAID and projects in Cuba in light of Mr. Gross’s arrest and sentencing?

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“The U.S. Government continues to stand with civil society in Cuba, as we do in other countries. Naturally, the arrest of Alan Gross prompted a review of our ongoing Cuba programs to provide for greater transparency, management, and oversight. This process is part of USAID’s commitment to adjusting and refining our assistance programs to best support Cuban civil society while developing closer links between our people and societies.”