Reportage on the Rossetti health centre in Nice, France. This rehabilitation centre is a hub of excellence with cutting-edge technology. The GRAIL (Gait Real-time Analysis Interactive Lab) is a complete solution devoted to walking anaylsis and training. It uses a double walkway complete with instruments, a motion capture system, three cameras and EMG, all synchronized with a virtual reality environment. The system enables an improvement in walking, whether pathological or not, involving fun and impelling exercises with which the patient interacts in real time. The patient is seen during GRAIL rehabilitation after a stroke.