WASHINGTON, April 8 -- The name of one of the world's most powerful men has resurfaced in one of the darkest scandals of modern history.

Bill Gates, the billionaire philanthropist who helped shape the digital age, is now preparing to testify before Congress in a widening investigation tied to the sprawling cache of documents known as the Epstein Files, a trove of emails, photographs, flight logs and personal communications that continues to expose the hidden networks of power surrounding the late financier Jeffrey Epstein.

The testimony, scheduled for June 10 before the House Oversight Committee, comes as lawmakers intensify scrutiny over the extent to which some of the world's most influential figures maintained relationships with Epst...