Hemophagocytic lymphohistiocytosis (HLH) is a rare and potentially fatal syndrome seen primarily in children. It is characterized by pathologic systemic hyper inflammation which in adults is easily overlooked due to non-specific clinical features. Most of the data available are on paedriatic population, making the diagnosis of HLH in adults challenging for the clinician. Here we report a case of HLH in a 48-year male who presented with pyrexia of unknown origin for 2 months but remained undiagnosed despite extensive workup. Due to a high index of suspicion, re-evaluation of bone marrow biopsy was done which showed hemophagocytosis, earlier reported as normal. It led to specific investigations, needed for establishing the diagnostic criteria of HLH. Even though chemotherapy was initiated, the patient did not survive. The aggressive nature of this disease makes it crucial for the physician to be aware of its signs and symptoms for the early diagnosis and immediate introduction of adequate treatment.