A 61-year-old female who had recently traveled to a Puerto Rico resort developed a fever and productive cough, followed ten days later by encephalopathy. On initial presentation to the emergency department, she was febrile. Neurologic examination was significant for disorientation and inattention. Serum labs were remarkable for leukocytosis (15.6 10*3/uL white blood cells), hyponatremia (131 mmol/L), and marked inflammatory response (erythrocyte sedimentation rate 120 mm/hr, procalcitonin 14.67 ng/mL, and c-reactive protein 468 mg/L). Chest radiograph showed a right perihilar opacity. Magnetic resonance imaging (MRI) of the brain revealed subcortical white matter fluid-attenuated inversion recovery (FLAIR) hyperintensities that did not enhance with gadolinium. There were multiple areas of restricted diffusion in the bilateral cerebral cortex and the splenium of the corpus callosum. Cerebrospinal fluid (CSF) analysis was blood-stained, with 5 white blood cells when corrected for erythrocytes, and with normal protein (33 mg/dL). CSF culture was negative. Polymerase chain reaction performed on the sputum was positive for Legionella pneumophila. With treatment of the pneumonia, the patient had rapid neurologic improvement. Repeat MRI five weeks after the initial presentation showed resolution of the corpus callosum lesion, with persistence of the subcortical FLAIR lesions.