Implantable cardioverter defibrillators (ICDs) are now an accepted and effective therapy for treatment of survivors of sudden cardiac death (SCD) and prevention of SCD in high-risk patients. Normal ICD function and delivery of therapy depends on appropriate sensing and detection of myocardial electrical potentials. Electromagnetic interference resulting in ICD malfunction is a well-documented phenomenon, however, there are less well-known external sources of interference, which may cause life threatening ICD malfunction. We report a unique case of repeated inappropriate ICD shocks in a ten-year old boy caused by the ICD sensing alternating current from an unexpected external source.