Abstract: On February 7, 2021, an employee working as a manager for a dental implant manufacturer called Coworker #1, dentist, to meet a client and a patient at his dental clinic at 9:00 a.m. The client will use the clinic to televise a surgery for training. Coworker #1 arrived at 8:56 a.m. and entered through the back door where he noticed a floor opening. At 8:58 a.m., the client and patient arrived at the front door. At 9:00 a.m., while waiting for the employee, they heard moaning and investigated. They saw the employee laying below the floor. She had come in the back door and fell through the 26-inch by 18-inch by 3-1/2-feet deep opening. Coworker #1 pulled the employee out and called for an ambulance. Coworker #2, building owner and clinic partner, said the employee texted him the night before about meeting, but he did not see the text until this day. Coworker #2 said Coworker #1 comes to the clinic unannounced every two weeks but never when they are closed. Coworker #2 arrived to obtain signed liability agreements. Coworker #2 said the construction company works in the building weekends performing renovations. This day, they were replacing ventilation ducts below the floor. Coworker #1 and Coworker #2 were puzzled why the employee came through the back, but she said she has entered that way before. Coworker #3, construction company owner/superintendent, said they have worked in the clinic for 1.5 years, only allowing access when their crews were not present, usually weekends. Coworker #4 was the only employee on site at the time. He arrived at 8:30 a.m. and opened the floor hatch before accessing the crawl space and traveling approximately 60 feet below the floor to replaced old ducts. He finished his work after 11:00 a.m. and exited the space at which time he first learned about the incident. He worked alone and didn't put out warning cones and caution tape since the building was unoccupied. The employee fractured her ribs and was hospitalized.