The road to Mr Gao's family home winds deep into the hills of northern Shaanxi province.
It's a bizarre and barren landscape, bisected by hundreds of valleys and gorges, like a giant, crumpled maze, dotted with poor villages.
Up a small, muddy path is the Gao family home. It's a line of traditional cave dwellings, large, simple rooms hewn into the hillside, and fronted by a facade of stone.
Before we visited our phone calls had been answered by two separate people who claimed they were "neighbours" watching the house as Gao Zhiyi had, they said, "gone away for a few days". It is not clear who these "neighbours" were.
When we arrived we found Gao Zhiyi, a farmer, busy at work outside his home, cutting stone slabs to lay paving outside his home.
There was no obvious sign of any Chinese security officials, but Gao Zhiyi was clearly nervous.
He asked us to be quick, saying: "Please go home soon, don't stay for too long. Because if the local authority finds out, it won't be nice".
Then he told us that Gao Zhisheng had called on 28 February or 1 March.
"He said he's quite well, everything's fine, and told the family not to worry," said Gao Zhiyi.
Asked if he was sure it was his brother's voice, he was firm: "It couldn't be wrong." And asked if Gao Zhisheng sounded healthy, Gao Zhiyi said "yes, very well".
But Gao Zhiyi said the conversation was brief, and his brother did not say where he was.
He claimed to have had three or four such calls since Gao Zhisheng vanished.
"I'm no longer worried. I just know that he's fine," he said.
It's impossible to say whether Gao Zhiyi did get the calls or whether he has been pressured to give this account to us.
From his family's poor beginnings Gao Zhisheng rose far. A decade ago he was named one of the 10 best lawyers in China by the government.
Gao Zhisheng has challenged China's leaders publicly
But he began to take on highly controversial cases, dealing with corruption, religious freedom, and - most sensitive of all - China's treatment of members of the banned Falun Gong movement.
He dared to challenge China's leaders publicly, writing open letters claiming they were "liable" for what he called the brutal and illegal persecution of Falun Gong members.
His law licence was taken away. He was convicted of inciting subversion, given a suspended sentence and released in 2006. The reason there are so many fears for his safety is that he claims to have been tortured during another detention in 2007.
An account of that torture, written by Gao Zhisheng and released by human rights groups just after he vanished last year, is graphic.
"Four electric batons started to shock me all over... when Wang started to shock my genitals, I begged him to stop," and he goes on, "he said 'You wrote to the American Congress. You traitor. This is China. The Communist Party's territory. Killing you is as easy as stepping on an ant'".
Gao Zhisheng was at his brother's house when police came for him, and Gao Zhiyi says the family were extremely concerned.
"We were worried about whether his life was under threat. Now we are a bit relieved but we can still do nothing."
It's tantalising, but Gao Zhiyi's story adds to the mystery about what's happened to Gao Zhisheng.
On Tuesday, in response to a question from the BBC about where the missing lawyer is, and whether he is alive and well, Chinese Foreign Minister Yang Jiechi said: "Gao Zhisheng was sentenced for subverting state power. His personal rights have been protected according to Chinese law. There is no so-called torture upon him."
It appeared that Mr Yang was referring to Mr Gao's original conviction, not a new one. And he did not address the issues of where Mr Gao was or what state of health he was in.
British Foreign Secretary David Miliband said he had raised the case, adding: "The widespread concern about it is an example of the global social conscience that increasingly exists. Foreign Minister Yang insisted to me on the integrity of the criminal justice and judicial procedures that exist in China".
To try to find Gao Zhisheng, we travelled further, to China's far west and the province of Xinjiang.
The tower blocks in Urumqi where Mr has allegedly been spotted
Earlier this year Chinese diplomats in America had suggested that Mr Gao was alive and "working" in Urumqi.
We went to the address where it has been rumoured Mr Gao had been spotted. It consisted of two tower blocks of modern flats, along with a busy hotel and many private businesses.
There was no sign of Mr Gao, no sign of any extra security, and everyone we showed his photograph to said they were sure they had never seen the missing lawyer.
So the questions remain. Where is Gao Zhisheng? Is he in good health? Why is China still saying nothing about his whereabouts?
Gao Zhisheng's wife and two children fled to America shortly before he was picked up last year. They and many others are still waiting to hear the answers.
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