They have come to Paddles, an after-hours sex club in Chelsea, not yet ready to end their evening. At around 4 on a Saturday morning, a time when most of the gay bars in New York have closed and locked their doors, a steady stream of young and middle-aged men, almost all shirtless and some stripped down to their boxer briefs, have found their way down a dark stairwell and into a maze of basement rooms, where the décor can best be described as fallout-shelter chic.