In December 2021, just weeks after he was elected as the second Black mayor in New York City’s history, Eric Adams took a surprise trip to Ghana.

He called it a “spiritual journey,” and the weeklong tour built on a story that had resonated deeply with voters. Mr. Adams visited slave trade sites and meditated on the remarkable arc that allowed a man whose ancestors left in shackles to return as the next leader of America’s largest city.

But federal prosecutors asserted this week that the trip was also at the center of a far more troubling story: a long-running bribery scheme in which Turkey plied Mr. Adams with more than $100,000 in luxury travel perks and illegal campaign contributions in exchange for political favors.

His spokesman insisted at the time that Mr. Adams had paid for the sojourn to Ghana. But prosecutors charged in their indictment that Turkish Airlines had secretly given Mr. Adams and his partner free business-class upgrades worth $12,000 — right after he agreed to lean on the Fire Department to prematurely approve safety permits for Turkey’s new consulate.