(CNN)It only took an hour.
Matthew Trevithick stepped out of the dorm where he was staying in Tehran and was on his way to buy a plane ticket back home when three people approached him from an unmarked Hyundai Sonata.
They asked if he was Matthew. When he said yes, they put him in the car and headed straight for Iran’s notorious Evin prison.
“Within an hour of standing on the street,” he said in an interview with CNN’s Anderson Cooper, “I’m sitting in an interrogation cell in the second floor of a specific building used by the intelligence services in Iran.”
He said the first thing interrogators asked was if he knew Jason Rezaian — the Washington Post journalist who, at the time, had already spent more than a year in an Iranian prison.
“I said of course, the whole world knows Jason Rezaian. Everybody knows that name,” Trevithick recounted. “He said he’s never leaving and neither are you.”
Trevithick, who was detained for 41 days, was one of five Americans that Iran released earlier this month.
The other four — Rezaian, Marine veteran Amir Hekmati, Christian pastor Saeed Abedini and Nosratollah Khosravi-Roodsari — were freed as part of a prisoner swap negotiated between the two countries.
The announcement of their releases came the same day that the International Atomic Energy Agency, the United Nations’ nuclear watchdog, announced Iran was in compliance with a July deal to restrict its nuclear program.
Iranian Foreign Minister Mohammad Javad Zarif told CNN’s Christiane Amanpour that although he believes those detained had “committed acts that were illegal,” he’s happy that the U.S. and Iran could reach an agreement.
“I think it was an important achievement that we all made together,” he said.
Trevithick went to Iran in September to study Farsi, according to a statement from his family.
He arrived back in Boston on January 17, his stepmother said.
Trevithick said that he was charged with personally trying to overthrow the Iranian government. Authorities also accused him of having access to bank accounts containing millions of dollars and knowing the locations of weapons caches that had secretly been planted around the country in preparation for a coup.
After he denied the charges, he was placed in solitary confinement for 29 days.
The room, he said, had a thin carpet covering the concrete floor.
It was about six-by-seven feet with a ceiling that ranged from 8 to twelve feet high — small enough for him to touch three sides at any time, he said.
There was neither a bed nor a pillow.
“That becomes your home. That is home.”
Despite spending nearly a month in solitary (something he thought was standard operating procedure after about a month), Trevithick said the scariest part of his ordeal was the final two hours before he was released.
It started when he was “violently” pulled from his cell and rushed to the prison’s basement.
“I could not believe, even spending 41 days there, could not believe what I was looking at,” he said. “I’m looking at a pitch black room with a single spotlight pointed at a chair with an ultra-high definition camera.”
A man walked in and stood behind a white sheet. The man running the camera is wearing a surgical mask.
“They say Matthew, Matt, this is your last chance. Admit why you are here. Admit that you are here to overthrow the government.”
The interrogators gave him a few minutes alone to contemplate what he was going to do.
When they came back, he said he looked straight into the camera and told them, “I’ve said everything I have to say.”
Though he said he was proud of his defiance, part of him also worried he had made a mistake.
“They kept saying, well, you’ve made a very bad decision,” he said.
Next, he said they threw him against the wall. Several minutes later he was rushed back to his cell, where lunch was waiting, and then was told to gather his belongings.
“You only collect all your things in Evin if you are leaving or if you’re being relocated,” he said.
He walked down the hallway, about 10 paces from his cell.
“I stop. My heart’s racing. My inner critic is louder than ever — great, Matt, now you’re about to reap what you’ve sown,” Trevithick told CNN.
To the left, the door towards the exit.
To the right, “deeper into the prison, towards solitary confinement cells and God knows what else,” he said.
“And oddly enough, they said turn left.”