  Narrow-band H$\alpha$ and [N {\sc ii}] images and high-dispersion
spatially-resolved echelle spectroscopy of the planetary nebula NGC 6891 are
presented. These observations show a great wealth of structures. The bright
central nebula is surrounded by an attached shell and a detached outer halo.
Both the inner and intermediate shells can be described as ellipsoids with
similar major to minor axial ratios, but different spatial orientations. The
kinematical ages of the intermediate shell and halo are 4,800 and 28,000 years,
respectively. The inter-shell time lapse is in good agreement with the
evolutionary inter-pulse time lapse. A highly collimated outflow is observed to
protrude from the tips of the major axis of the inner nebula and impact on the
outer edge of the intermediate shell. Kinematics and excitation of this outflow
provide conclusive evidence that it is deflected during the interaction with
the outer edge of the intermediate shell. At the same time, both the kinematics
and the morphology of the intermediate shell appear to be affected by this
interaction.
