Blandine Briere spoke to her brother Benjamin every day as he travelled though Iran in the winter of 2019.
He would tell his sister of the places and people he was meeting during the latest leg of his world trip, dutifully chronicled on Instagram as he journeyed through Iran's mountain ranges in a renovated van.
Now, they can only communicate every three to four weeks, discussion stifled as guards watch on at Mashhad central prison, in the north-east of the country.
Briere, 36, has been held for more than two years in a facility notorious for secret executions and human rights abuses.
The French national was sentenced by an Iranian court to eight years in jail after being convicted of spying charges, his lawyer said in January.
“He is exhausted,” Ms Briere told The National from her home in France.
“At the beginning he was strong, and now he doesn't have any hope. He is exhausted and it’s hard to see the light.”
The disturbing reality inside Iran's prisons has come back into the spotlight amid the continuing protests that have swept the country.
These were sparked by the death of Mahsa Amini, 22, on September 16, while in the custody of the country's morality police. She had been detained three days earlier for wearing her hijab “improperly”.
Last Saturday, fire raged through Evin, the country's most notorious prison, in Tehran. The blaze killed at least eight people according to judiciary officials.
Evin was the site of mass executions in 1988, during a nationwide campaign in which thousands of political prisoners were killed.
On Tuesday, Amnesty International said the fire was started by authorities' unlawful use of force against prisoners, with shooting recorded more than an hour before the fire allegedly began.
Authorites said it was the result of a dispute among inmates.
Solitary confinement and night interrogation
The last time Ms Briere spoke to her brother, he wasn't aware of what was going on outside his prison walls. The only time he can leave his cell is to walk in the 10-square-metre prison yard.
“Two weeks ago he didn't really know what was happening outside. I tried to explain it to him because there is only propaganda inside the prison, he wasn't aware of what was happening,” she said.
“Our conversations are recorded so I couldn't give details.
“We completely defend what is happening [the protests], but we see it has made communicating with him more complicated.”
He spent months in solitary confinement, where prisoners can be taken for interrogation at any time.
Now, he is regularly moved from one overcrowded cell to another — where upwards of 30 people are crammed together and the lights are never turned off.
“It's a kind of psychological torture,” said Ms Briere. “It's unsanitary … He doesn't have the strength any more to talk to people. He is imprisoned with people with death sentences, people who fight with guards. There is physical abuse, psychological torture, it's really hard.”
“He is trying every day to fight for his rights. Every day, he asks if he can call his family, for his right to use the shower, to go outside.”
Windowless cells and blindfolded visits
Conditions are notoriously harsh at Evin, where the country's most prominent dissidents, foreign nationals and activists are held.
Activists based in Iran have said hundreds of people arrested during this wave of protests are being detained at the facility, as well as at secret detention centres.
The National has been told of horrific conditions in Evin's solitary confinement cells, where Belgian humanitarian aid worker Olivier Vandecasteele was held for months after his arrest this year on espionage charges.
Since August, his exact location is unknown, but The National has been told he has been kept in a windowless basement cell.
Mr Vandecasteele's health has deteriorated significantly since his arrest, family and friends have said. He has been struck by regular infections and dental problems.
“He ate potatoes, lentils and sugar — that's it,” a source close to his case said of his first four months in jail.
Mr Vandecasteele has since also been allowed fruit and vegetables, said the source.
“He has seen a doctor twice, but the first one didn't speak any English. Now they've said medicine went missing.”
He was only allocated a bed after four months of imprisonment.
Mr Vandecasteele, who, served as the director of the Norwegian Refugee Council's Iran office before his arrest in February, has yet to be charged with a crime.
He has been allowed four visits from the Belgian ambassador, during which he was blindfolded.
“He is being held for nothing,” the source said. “The UN says 15 days of isolation is torture, and this has been eight months.”
Ana Diamond, 26, was arrested in 2016, sentenced to death and held in solitary confinement for 200 days in Evin. She was allowed one visit and phone call during her month in the prison's public ward.
Ana, a British-Iranian, who had Finnish citizenship at the time of her arrest, said psychological abuse, including mock executions, was a common feature of life inside.
“The torture was highly psychological because they don't want visual remnants of that time on your body in case you went and showcased it to the media,” she told The National from Oxford, where she now studies.
“They definitely think it through, They want put you under enough pressure and psychological terror to do what they want but not so much that you can go around indicting them on it.”
The prison is often referred to as “Evin University” due to its highly educated inmates, who would hold weekly lectures and seminars for other inmates to pass the time.
Others wrote books, smuggling out a page at a time in rare visits with relatives.
“We made the most out of the least we had,” Ms Diamond said.
“Evin prison's history traces well before the Islamic Republic was established, so the cruelty suffered at Evin is a recurrent event in history and many would like to see that place shut down.
“However, one needs to also be realistic and understand that an escalating fire ravaging through parts of the prison, followed by gunshots and explosions, can only mean bad news.”