Active sunspot group n° 4567 was observed with high angular magnification on Sept. 2, 1984, using the instrument FPSS at Meudon Observatory. Within the sunspots umbrae, the longitudinal magnetic field shows a collection of small elements down to the limit of resolution of around 600 km. Between the trailing and leading spots, there were very sharp gradients, both in magnetization (450 gauss over 1000 km) and in Doppler velocity (350 m s-1 over 1 000 km). The line defined by these gradients was the location of a flare. Evershed driving forces may be responsible for building up these gradients and flare.