  We propose an integrable model of the spin-1/2 Heisenberg chain coupled to
two impurity moments. With the open boundary conditions at the impurity sites,
the model can be exactly solved for arbitrary impurity spin and arbitrary
exchange constants between the bulk and the impurities. The absence of
redundant terms in the hamiltonian makes the model very reasonable. The
hamiltonian is diagonalized via algebraic Bethe ansatz. It is found that the
impurity spins can only be screened (partially for $S>1/2$) for
antiferromagnetic coupling between the impurity and the bulk. Otherwise the
impurity spins can not be screened. The residual entropy of the ground state
and the Kondo temperature are also derived explicitly based on the
thermodynamic Bethe ansatz and the local Fermi liquid theory.
