(Bloomberg) -- They’d come a long way together, from teenage mathletes to MIT frat brothers to crypto billionaires.

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Now the feds were closing in on both — and one was going to turn on the other.

“We can make this work,” Sam Bankman-Fried said over Signal, an encrypted messaging app.

Gary Wang didn’t reply.

The time: mid-November, days after FTX collapsed. The place: a $40 million penthouse in the Caribbean — last stop, US authorities say, on a trail of lies stretching back to the very beginning of the men’s FTX cryptocurrency empire.

Wang, FTX’s software savant and ultimate secret-keeper, was holed up in one of the five bedrooms of the oceanfront aerie where he worked with Bankman-Fried and eight others. He emerged, with two lawyers who’d flown in from New York beside him. Wang dropped the news he was leaving.

“I sort of said, ‘Have you fully made up your mind or do you want to talk about it?’” Bankman-Fried recalled of his final conversation with Wang, in an interview at his parents’ California home. “He said he had made up his mind and that was that.”

What Wang didn’t say was that he was going to flip on his friend, FTX’s famous, and now infamous, front man.

Those final moments in Nassau — Bankman-Fried’s urgent Signal message would follow — marked a turning point for both men. Their break will go down as a signature moment in the spectacular rise and even more spectacular fall of FTX, once one of the world’s largest cryptocurrency exchanges.

For a decade and a half, nearly all their adult lives, Bankman-Fried and Wang traced an arc of mind-blowing success together. Bankman-Fried sold himself as the crypto wunderkind willing to spend billions to save humanity. Wang worked in the shadows -- largely a mystery to the wider world.