First, a health inspector spotted several suitcases. Then she noticed an unusual stash of clothing, food and bedding. A young woman who was supposed to be a massage therapist spoke little English and seemed unusually nervous. The inspector reported her findings to police. They would eventually learn that her suspicions were right: The women were not just employees: They were living in the day spa, sleeping on massage tables and cooking meals on hot plates in the back. Some of them had had their passports confiscated. The inspector’s suspicions prompted a sprawling investigation across four Florida counties and two states — Florida and New York — over nearly eight months, resulting in the disruption of what authorities say was a multimillion-dollar human-trafficking and prostitution operation.