  We report on the detection of three transiting small planets around the
low-mass star LP 358-499 (K2-133), using photometric data from the Kepler-K2
mission. Using multiband photometry, we determine the host star to be an early
M dwarf with an age likely older than a Gigayear. The three detected planets
K2-133 b, c, and d have orbital periods of ca. 3, 4.9 and 11 days and transit
depths of ca. 700, 1000 and 2000 ppm, respectively. We also report a planetary
candidate in the system (EPIC 247887989.01) with a period of 26.6 days and a
depth of ca. 1000 ppm, which may be at the inner edge of the stellar habitable
zone, depending on the specific host star properties. Using the transit
parameters and the stellar properties, we estimate that the innermost planet
may be rocky. The system is suited for follow-up observations to measure
planetary masses and JWST transmission spectra of planetary atmospheres.
