  We show that final state interactions are important in shaping Dalitz plots
for the decay $D^+ \rar K^- \p^+ \p^+$. The theoretical treatment of this
reaction requires a blend of several weak and hadronic processes and hence it
is necessarily involved. In this talk we present results from a calculation
which is still in progress, but has already unveiled the role of important
dynamical mechanisms. We do not consider explicit quark degrees of freedom and
our study is performed within an effective hadronic framework. In spite of the
relatively wide window of energies available in the Dalitz plot for the $D^+$
decay, we depart from $SU(3)\times SU(3)$ chiral perturbation theory and extend
its range by means of unitarization. Our present results, which concentrate on
the vector weak vertex, describe qualitative features of the modulus of the
decay amplitude and agrees well with its phase in the elastic region.
