A prosthetic mitral valve replacement is a major surgical procedure that patients may undergo when experiencing severe refractory symptoms. When a patient presents with progressive lethargy, the differential diagnosis should be broadened, and appropriate imaging should be performed, particularly in the context of a significant surgical history. This may reveal severe underlying pathology, such as a chronically infected valve with a ruptured bioprosthetic mitral valve left wide open. We present the case of a 78-year-old female with a history of prior mitral valve repair followed by bioprosthetic mitral valve replacement and a remote episode of septic bacteremia requiring intensive care unit admission, who subsequently presented to her cardiologist with a 3-month history of worsening lethargy and declining functional capacity. A transesophageal echocardiogram ordered by her cardiologist revealed severe bioprosthetic mitral valve leaflet dehiscence with 4+ mitral regurgitation and mobile vegetations consistent with subacute infective endocarditis. Blood cultures obtained at the time of presentation grew Streptococcus viridans, which was considered the likely causative organism. The patient was initiated on broad-spectrum intravenous antibiotics and subsequently underwent successful bioprosthetic mitral valve re-replacement at a tertiary referral center, with an uncomplicated postoperative course and excellent functional recovery. This case exemplifies the importance of avoiding early closure in clinical decision-making and remaining open-minded when pursuing diagnostic testing for conditions for which a patient has risk factors, even in the absence of characteristic symptoms.