Peloton Flew High, Fell Fast

When hedge-fund chief Ron Beller's investments in U.S. mortgages turned against him, he got a rude awakening to Wall Street's unsentimental ways. Bankers who had vied for his business reeled in credit lines and seized the fund's assets. In a matter of days, Peloton Partners LLP, once one of the world's best-performing hedge-fund operators, lost some $17 billion.

At one point during the ordeal, Mr. Beller, a 46-year-old with two decades of high-finance experience, collapsed from exhaustion, according to people familiar with the matter.

From the U.S. to Europe, the turmoil in financial markets is leaving behind stories like Mr. ...