Cyst or thrombus formation in the left ventricular outflow tract of a normal heart is very rare. We present a case of a male who presented with a major stroke and was found to have a freely mobile cystic mass in the left ventricular outflow tract, with an otherwise completely normal heart. He had some risks factors for hypercoagulability (reduced protein C activity and raised fibrinogen), but only received aspirin therapy due to his stroke severity (haemorrhagic transformation). Once his brain imaging suggested it was safe to proceed, repeat imaging showed the mass had gone, so cardiac surgery was avoided. What was it and where did it go?