Mr Gershkovich, a 32-year-old US citizen who works for the Wall Street Journal (WSJ), has now been held for 100 days.

"The conviction rate in Russia is almost 100%," one of his colleagues pointed out during an interview with his parents.

"Exactly," his mother Ella Milman replied. "Especially in cases like that."

Is there anything that gives her hope, Shelby Holliday asked.

"No," Ms Milman replied.

Mikhail Gershkovich, the journalist's father, said there was "absolutely nothing" he can do, even though he would "like a chance to do anything".

His son, who was formally charged with spying in April, is being held at the notorious Lefortovo prison in Moscow and faces up to 20 years behind bars if convicted.

His newspaper vehemently denies the accusations against him, and he was accredited by the Russian Foreign Ministry.

He is being "wrongfully detained", US Secretary of State Antony Blinken has said.

Last month, a new appeal against his pre-trial detention was rejected by a Moscow court.

His parents, who left the Soviet Union for the United States in 1979, were there and able to speak to him as he stood in a glass box.

"Seeing him just brought him a little bit back to me," his father told the WSJ. "Physical closeness made it a little more bearable."

"I was just beside myself - so happy," his mother said. "We were smiling and laughing."

She said she then remembered her child was in a courtroom.

"My son was in this aquarium, in this cage, and I had to realise where I was because I lost myself in that conversation. I was so happy to see him."

Mr Gershkovich's sister, Danielle, said she watched her parents talking to him in the Moscow courtroom on video.

"I was just smiling," she said. "I just couldn't wipe the grin off my face. I'm just holding on to those things that are bringing me joy right now."

But the appeal was lost and his parents travelled back to Philadelphia.

"It was even harder to leave him there than it was the first time," his mother said.

Ms Milman is hoping the American authorities can make a breakthrough.

"I rely on President Biden's promise to do whatever it takes to bring Evan back," she said.

"I rely on his team, on their expertise. He's an American boy. Bringing him back is a team effort."

Danielle Gershkovich said the family was receiving lots of support.

"I just know we're not alone in this," she said.