  We present a HI synthesis imaging study of NGC 864 (CIG 96), a spiral galaxy
well isolated from similarly sized companions, yet presenting an intriguing
asymmetry in its integral HI spectrum. The asymmetry in the HI profile is
associated with a strong kinematical perturbation in the gaseous envelope of
the galaxy, where at one side the decay of the rotation curve is faster than
keplerian. We detect a small (M(HI) = 5 x 10^6 Msun) galaxy with a faint
optical counterpart at around 80 kpc projected distance from NGC 864. This
galaxy is probably not massive enough to have caused the perturbations in NGC
864. We discuss alternatives, such as the accretion of a gaseous companion at a
radial velocity lower than the maximum.
