Emergency medical services received a telephone call from a mother reporting that her three-month-old daughter “turned blue and then stopped breathing” after a prolonged period of crying. On arrival, paramedics found an infant making minimal respiratory efforts with a heart rate of 100 beats/min. Bag-mask ventilation was initiated on the scene. During transport to hospital, she had no spontaneous respiratory effort. Endotracheal intubation was performed and the infant was admitted to the intensive care unit. On admission, pH was 6.84, pCO 2 102 mmHg, and serum lactate 28 mmol/L. Chest radiography demonstrated moderate pulmonary edema. Her medical record revealed a two-week stay in the intensive care unit following birth for treatment of neonatal abstinence syndrome because her mother had a history of prescription opioid abuse and had been enrolled in a methadone maintenance treatment (MMT) program throughout pregnancy. The baby had been treated with oral morphine and formula feeding was initiated because the mother did not wish to breastfeed. A urine toxicology screen for methadone was collected from the infant 30 min after admission. The result was positive and a naloxone infusion was initiated. Despite aggressive ventilator and hemodynamic support, she developed fixed, dilated pupils 8 h later and was eventually declared brain dead. A report was made to child welfare authorities because of the positive toxicology screen and the death was reported to the medical examiner, who initiated an inquiry. During investigations, the mother, who was taking 120 mg/day of methadone and had ‘carry privileges’, admitted to adding “a little bit” of methadone to her daughter’s formula on three or four occasions of extreme fussiness, because it “helped her to relax”. Autopsy revealed significant cerebral and pulmonary congestion and edema, and no evidence of previous or recent trauma. Analysis of material collected at autopsy confirmed the presence of methadone. The methadone intoxication diagnosis was noted on the death certificate.