It sounded like a perfectly grand idea.

In April 2008, the New York City comptroller, William C. Thompson Jr., as investment officer for the city’s multibillion-dollar pension funds, stood shoulder to shoulder and beaming with the Protestant leader Ian Paisley and the Catholic leader Martin McGuinness and announced that the city would pour $150 million into once war-torn precincts of Northern Ireland.

It is, Mr. McGuinness said, “the ordinary people of the United States investing in the ordinary people of the North.”

Or not, as the case turned out.

Twenty months later, not a penny of that pension money had been invested in Northern Ireland. The new comptroller, John C. Liu, decided to pull the plug on the investment in January 2010.

The highly unusual decision to shut this ballyhooed investment fund carried a cost. The city paid a $3 million management fee to Emerald Infrastructure Development Fund, the little-known group of investors that had been chosen by Mr. Thompson’s office to invest in Ireland. And Emerald Infrastructure, in turn, paid $250,000 of the city’s money to William Howell, an old friend and generous campaign contributor to Mr. Thompson.