  We present a multiwavelength study of the nucleus, environment, jets, and
hotspots of the nearby FRII radio galaxy 3C 321, using new and archival data
from MERLIN, the VLA, Spitzer, HST, and Chandra. An initially collimated radio
jet extends northwest from the nucleus of its host galaxy and produces a
compact knot of radio emission adjacent (in projection) to a companion galaxy,
after which it dramatically flares and bends, extending out in a diffuse
structure 35 kpc northwest of the nucleus. We argue that the simplest
explanation for the unusual morphology of the jet is that it is undergoing an
interaction with the companion galaxy. Given that the northwest hotspot that
lies >250 kpc from the core shows X-ray emission, which likely indicates in
situ high-energy particle acceleration, we argue that the jet-companion
interaction is not a steady-state situation. Instead, we suggest that the jet
has been disrupted on a timescale less than the light travel time to the end of
the lobe, $\sim 10^6$ years, and that the jet flow to this hotspot will only be
disrupted for as long as the jet-companion interaction takes place. The host
galaxy of 3C 321 and the companion galaxy are in the process of merging, and
each hosts a luminous AGN. As this is an unusual situation, we investigate the
hypothesis that the interacting jet has driven material on to the companion
galaxy, triggering its AGN. Finally, we present detailed radio and X-ray
observations of both hotspots, which show that there are multiple emission
sites, with spatial offsets between the radio and X-ray emission.
