Flickering Lights, Strange Music and a Ghost at a Brooklyn Bar. Maybe.

On a dark morning in September 2006, Miguel Vargas arrived for work at a Brooklyn restaurant called Sweetwater. He unlocked and lifted the security gate, took two steps inside and saw a woman in profile walking across the dining room toward a basement stairwell.

She was middle-aged with gray hair and dressed in white, like a wedding dress, he said, but n…