On a recent Saturday night, more than a dozen people found themselves in the industrial wilds of Long Island City, Queens, looking for a line of yellow paint.

They had been invited by email, and when they arrived at the appointed intersection, at 11 p.m., they were instructed by text to follow the paint, as though in Oz, until the end. “The doorman awaits,” the text said. “Be discreet.”

It added: “Bring a sunflower if you see one.”

The yellow line was easy to miss if you weren’t looking. A mere dribble at points, it veered away from the art venues and coffee shops of Long Island City and into a dark warren of warehouses. It ran past delivery trucks and Dumpsters and, yes, an improbable patch of sunflowers. Then it stopped, at an overpass.

Or seemed to stop. At the overpass, it ran up a retaining wall. A man waved from above: the doorman. The guests clambered up, clinging to a chain-link fence, and at the top, they took in the view. Tall weeds swayed, growing high between the railroad tracks. The Manhattan skyline twinkled.