  Based on the atomic-hydrogen (HI) observations using the Five-hundred-meter
Aperture Spherical radio Telescope (FAST), we present a detailed study of the
gas-rich massive S0 galaxy NGC 1023 in a nearby galaxy group. The presence of
an HI extended warped disk in NGC 1023 indicates that this S0 galaxy originated
from a spiral galaxy. The data also suggest that NGC 1023 is interacting with
four dwarf galaxies. In particular, one of the largest dwarf galaxies has
fallen into the gas disk of NGC 1023, forming a rare bright-dark galaxy pair
with a large gas clump. This clump shows the signature of a galaxy but has no
optical counterpart, implying that it is a newly formed starless galaxy. Our
results firstly suggest that a massive S0 galaxy in a galaxy group can form via
the morphological transformation from a spiral under the joint action of
multiple tidal interactions.
