Nitrous oxide is a highly lipid-soluble molecule, which can produce euphoria and calming effects through noncompetitive antagonism of the N-methyl-D-aspartate (NMDA) glutamate receptor and agonism of the y-aminobutyric acid (GABA) A receptor. It can also produce toxicities likely through inactivation of methylcobalamin (vitamin B12) with subsequent neurological, psychiatric, and other sequelae that may be mistaken for other clinical entities. We present a classic presentation of nitrous oxide toxicity, which was missed and urgently referred to infectious diseases with concerns for an infectious neuromyelitis. Knowing the constellation of symptoms and findings and maintaining a high index of suspicion are key to diagnosing nitrous oxide toxicity, which can otherwise easily be missed. Cessation of use, B12 supplementation, and supportive measures such as occupational and physical therapy are helpful for maximizing long-term beneficial outcomes.