In the emergency room of a large public hospital in São Paulo, resident Lucas Ramos begins to see mysterious clinical clues appear in front of patients. But none of them come with a ready-made diagnosis: to understand what is happening, he needs to think fast and reason like a doctor — even when veterans like Drs. Fernando Nogueira and Dr. Renato Medeiros doubt him. From a hard-to-detect Meningitis to a silent abdominal bleed and the rare Takayasu arteritis, each case tests his limits in the pediatric emergency department, the ward, and the General Surgery Department. Between strict protocols and skeptical colleagues, Lucas must prove that his discoveries come from dedication and insight — before a complex case slips through the diagnostic cracks.