GEOFF BENNETT: China recently took a rare step.

It released a detainee at the request of the U.S.

Pastor Ezra Jin Mingri was picked up by Chinese authorities last October, one of dozens of Christians targeted by the Chinese Communist Party, which only allows authorized churches to serve China's estimated 80 million Christians.

Pastor Jin, as he is known, is now free after a personal request by President Trump to Chinese leader Xi Jinping.

He and his daughter spoke to our Nick Schifrin, who begins his story in an underground church in Beijing.

NICK SCHIFRIN: On the sixth floor of a Beijing apartment building, an unmarked door, inside, a secret church for those prohibited from praying in public.

It's 2019, and Xu Yonghai was the pastor of the Holy Love Fellowship, a congregation of China's most vulnerable Christians, critics of the communist government, his sanctuary also his apartment and bedroom.

There was good reason for secrecy.

In 2014, he and his entire parish was detained.

XU YONGHAI, Pastor, Holy Love Fellowship (through translator): We were arrested because we defended the rights of other churches.

NICK SCHIFRIN: Christian activists say the government has demolished thousands of unsanctioned churches and targeted their parishioners, including the largest unsanctioned church, Zion.

In 2018, Beijing detained its leader, Ezra Jin Mingri, for refusing to install facial recognition cameras.

The church was forced to go mostly virtual, which meant it grew dramatically from 1,500 to more than 10,000 worshipers across 40 cities.

Last year, Beijing's security officials came for Zion again, detaining church leaders during a retreat for elderly church members.

It was one of Beijing's largest ever crackdown on Christians, including Pastor Ezra Jin Mingri's second detention.

DONALD TRUMP, President of the United States: I think he's giving very serious consideration to the pastor.

NICK SCHIFRIN: In May, President Trump told reporters he had brought up the case during meetings with Xi in Beijing.

And then, last month, after 266 days in detention, Jin was freed into the embrace of his daughter Grace, who hadn't seen him because he was banned from leaving China more than five years ago.

I spoke to them in our studio last month.

GRACE JIN DREXEL, Daughter of Pastor Ezra Jin Mingri: When I saw him, I didn't even recognize him.

We haven't seen each other in the last six years for me.

So it's just incredible.

When I first heard in October, we were like deer in the highlights.

We just didn't know what to do, and just shocked, and there was always this sense of like the world was collapsing, and we are in a sense competing or trying to have the second most powerful nation in the world to change their policies or change their decisions, and that that seemed impossible.

That seemed so insurmountable.

NICK SCHIFRIN: Can you tell me about your detention?

What were the conditions inside?

PASTOR EZRA JIN MINGRI, Founder, Zion Church (through translator): The conditions were obviously very bad.

The food and 30 or so people living in a tight space, there isn't any freedom.

We just sit on a stool.

We need to raise our hands to ask for permission to walk around.

All my communications were cut off.

NICK SCHIFRIN: When Beijing police targeted Zion, they first charged parishioners and Pastor Jin with -- quote -- "illegally using information networks."

Beijing ended up prosecuting them for operating an illegal business and fraud.

There are Chinese government-approved ministries that display banners like this one, implement the basic direction of the Communist Party's religious work.

But Chinese President Xi Jinping has long described minorities and their cultures and religions as threats to the stability of the Communist Party and therefore the country.

It's not only Christians.

In 2017, Beijing set up what activists called concentration camps for Muslim Uyghurs.

It was part of a crackdown on Uyghur language and culture and later became forced labor.

On the last day of the first Trump administration, the U.S.

accused Beijing of genocide.

PASTOR EZRA JIN MINGRI (through translator): Chinese society is a totalitarian society.

Therefore, the party is in charge of everything.

Ethnic minorities and various religious beliefs, and even some opinionated people, as well as independent intellectuals, are facing huge pressure in China, even oppression.

NICK SCHIFRIN: Do you believe that your release was the product of a personal appeal by President Trump to Xi Jinping?

PASTOR EZRA JIN MINGRI (through translator): Of course, only if the American president said so in person and Chinese Chairman Xi decided that this could happen.

NICK SCHIFRIN: Today, eight Zion Church leaders remain imprisoned.

Their families are desperate for international help, but Beijing vows to put them on trial.

That's a fate that Grace Drexel feared for her and her father.

WOMAN: Free Pastor Jin.

NICK SCHIFRIN: This past May, Grace Jin helped lead a Washington, D.C., rally, calling for Beijing to release its prisoners.

Her father's detention was especially difficult because, when he was detained, she was pregnant.

GRACE JIN DREXEL: I told my father a week before that we were pregnant.

And then my dad got detained.

My father's been detained this whole time.

And now the baby's about to be born and he is still detained.

My father's situation, we were looking at very easily 15 years in prison.

And so in my mind, if my father was in there for 15 years, and we're not allowed to see him or not allowed to communicate with him, like, we would -- that might have been the end of -- he knew that I was pregnant.

I was able to tell him about that a week actually before that he was arrested.

But we were still first trimester, and we were not sure about whether -- the tremendous pressure that we were also going through, on whether the baby would come be with us.

NICK SCHIFRIN: But the baby is with them.

His name is Ezra, named for his grandfather.

GRACE JIN DREXEL: So incredibly, incredibly grateful and so incredibly just without -- like, I'm without words.

I don't really know how to explain this overwhelming opportunity or joy or miracle that we have seen.

NICK SCHIFRIN: It's very important for you, isn't it, to be with your grandson?

PASTOR EZRA JIN MINGRI: Yes.

NICK SCHIFRIN: What change, Pastor Jin, would you like to see in China for your grandson's generation?

PASTOR EZRA JIN MINGRI (through translator): I think that many imprisoned Christians love their country and motherland.

I hope that in China's future people can worship God without fear.

NICK SCHIFRIN: But there is still fear, and Chinese Christians often have to hide their faith.

For the "PBS News Hour," I'm Nick Schifrin.