Stephen Hemsley hasn’t been CEO at UnitedHealth Group in nearly a decade yet he’s never really left. Hemsley, 72, has remained chairman and a major shareholder in the health care behemoth — and now is back in the CEO

Stephen Hemsley ran UnitedHealth Group for more than a decade. It's a different company after four years with Andrew Witty in charge.

UnitedHealthcare stock plunged again on Thursday after a new report in the WSJ said the company is facing a Medicare fraud probe.

The reported probe adds to a string of recent setbacks that have erased more than half, or over $300 billion, from its market value since November.

UnitedHealth faces valuation reset amid CEO change, regulatory probes, and cost overruns. Click here for a full analysis of UNH stock.

Former CEO and current chairman Stephen Hemsley is stepping back into the top job following the abrupt resignation of Andrew Witty, UnitedHealth said.

UnitedHealth is bringing back former CEO Stephen Hemsley, as the insurance giant faces spiraling costs and a criminal investigation into its Medicare billing.

As CEO for more than a decade, Stephen Hemsley built up UnitedHealth Group, now a $400 billion healthcare behemoth. With his return to the top job, the company will learn whether his playbook still works.