  We report results of the eclipse mapping analysis of an ensemble of light
curves of HT Cas. The fast response of the white dwarf to the increase in mass
transfer rate, the expansion rate of the accretion disc at the same time, and
the relative amplitude of the high-frequency flickering indicate that the
quiescent disc of HT Has has high viscosity, alpha ~ 0.3-0.7. This is in marked
disagreement with the disc-instability model and implies that the outbursts of
HT Cas are caused by bursts of enhanced mass-transfer rate from its donor star.
