Using data obtained during the RATS-Kepler project, we identified one short-duration flare in a 1 h sequence of ground-based photometry of the dwarf star KIC 5474065. Observations made using Gran Telescopio Canarias show that it is a star with an M4V spectral type. Kepler observations made using 1 min sampling show that KIC 5474065 exhibits large-amplitude (δF/F > 0.4) optical flares which have a duration as short as 10 min. We compare the energy distribution of flares from KIC 5474065 with that of KIC 9726699, which has also been observed using 1-min sampling, and ground-based observations of other M dwarf stars in the literature. We discuss the possible implications these short-duration, relatively low-energy flares would have on the atmosphere of exoplanets orbiting in the habitable zone of these flare stars.