The use of subcutaneous implantable cardioverter defibrillators has been steadily increasing during the last decade. They serve multiple benefits, including freedom from lead-related complications and preservation of vasculature. However, subcutaneous implantable cardioverter defibrillators---specific complications have been starting to emerge and are currently threatening the potential benefit achieved by subcutaneous implantable cardioverter defibrillators over transvenous implantable cardioverter defibrillators. We present a case of T wave over sensing during sinus rhythm, resulting in an inappropriate shock therapy leading to malignant tachycardia in a patient with generation three subcutaneous implantable cardioverter defibrillators.