  We present a multiwavelength study of IC 860, a nearby post-starburst galaxy
at the early stage of transitioning from blue and star-forming to red and
quiescent. Optical images reveal a galaxy-wide, dusty outflow originating from
a compact core. We find evidence for a multiphase outflow in the molecular and
neutral gas phase from the CO position-velocity diagram and NaD absorption
features. We constrain the neutral mass outflow rate to be ~0.5 M$_{\odot}/$yr,
and the total hydrogen mass outflow rate to be ~12 M$_{\odot}$/yr. Neither
outflow component seems able to escape the galaxy. We also find evidence for a
recent merger in the optical images, CO spatial distribution, and kinematics,
and evidence for a buried AGN in the optical emission line ratios, mid-IR
properties, and radio spectral shape. The depletion time of the molecular gas
reservoir under the current star formation rate is ~7 Gyr, indicating that the
galaxy could stay at the intermediate stage between the blue and red sequence
for a long time. Thus the timescales for a significant decline in star
formation rate ("quenching") and gas depletion are not necessarily the same.
Our analysis supports the quenching picture where outflows help suppress star
formation by disturbing rather than expelling the gas and shed light on
possible ongoing activities in similar quenching galaxies.
