Fethullah Gulen has been called Turkey's second most powerful man. He is also a recluse, who lives in self-imposed exile in the US.
An apparent power struggle between his followers and those around the Turkish Prime Minister, Recep Tayyip Erdogan, has reached a new pitch of intensity and loathing.
Since arriving in the US in the late 1990s, Mr Gulen, 74, has not given a single broadcast interview. What rare communication there has been with the media has almost exclusively been conducted via email.
But now, the BBC has had exclusive access to the Muslim cleric. I travelled with Guney Yildiz from the BBC Turkish Service to a remote part of Pennsylvania to meet the man.
In the interview, Mr Gulen denied using his influence to start investigations into alleged corruption among senior members of Mr Erdogan's AK Party which have led to a number of police commissioners being sacked and to some of Mr Erdogan's allies being arrested.
Two moments stood out from my interview with Mr Gulen. Neither had anything to do with what he said.
The first occurred as our camerawoman, Maxine, was making some last-minute adjustments to the lighting. Mr Gulen waved his hand wanly, and a man rushed forward from the chairs arranged on one side of the room. In his haste, he stumbled over the carpet. He was Mr Gulen's personal physician.
He took the blood pressure of his elderly charge, before poking, one-handed, a pill from its packet and giving it to his patient to chew. The testing and dispensing routine would be repeated later in the interview.
The second incident happened at the end of our long conversation, which was prolonged by the consecutive translation. Moments after Mr Gulen stood up, he swayed. One of his 13 followers in the room caught him by his shoulders, and righted him.
Fethullah Gulen may be, as the former US ambassador to Turkey James Jeffrey told me, Turkey's second most powerful man - an Islamic cleric who sits atop a movement with perhaps millions of followers, worth perhaps billions, with a presence, often through its high-achieving schools, in 150 countries.
But Mr Gulen's own physical capabilities appear to be ebbing. He has, we were told, a series of chronic ailments, and is recovering from an upper respiratory disorder. Indeed, just before the interview, one of his closest colleagues told me it had been on the cusp of being cancelled.