  We introduce and study one parameter family of integrable quantum field
theories. This family has a Lagrangian description in terms of massive Thirring
fermions $\psi,\psi^{\dagger}$ and charged bosons $\chi,\bar{\chi}$ of complex
sinh-Gordon model coupled with $BC_n$ affine Toda theory. Perturbative
calculations, analysis of the factorized scattering theory and the Bethe ansatz
technique are applied to show that under duality transformation, which relates
weak and strong coupling regimes of the theory the fermions
$\psi,\psi^{\dagger}$ transform to bosons and $\chi,\bar{\chi}$ and vive versa.
The scattering amplitudes of neutral particles in this theory coincide exactly
with S-matrix of particles in pure $BC_n$
  Toda theory, i.e. the contribution of charged bosons and fermions to these
amplitudes exactly cancel each other. We describe and discuss the symmetry
responsible for this compensation property.
