We report a case of unanticipated difficult endotracheal intubation secondary to an abrupt onset of difficulty in opening the mouth in an anesthetized adult. A female aged 76 years with American Society of Anesthetists risk Class IV E with an apparently normal preoperative temporomandibular joint was scheduled for emergency laparotomy. Following rapid sequence induction, and muscle relaxation with rocuronium, the anesthesiologist noticed lock-jaw when intubation was attempted. She was ventilated with nasopharyngeal airway, but was progressively desaturating. An emergency tracheostomy was performed. Unfortunately, she sustained cardiac arrest and could not be revived. The complication of the lock-jaw is a nightmare to airway management, especially in an unprepared situation.