  The two-point correlation function of the stress-energy tensor for the
$\Phi_{1,3}$ massive deformation of the non-unitary model ${\cal M}_{3,5}$ is
computed. We compare the ultraviolet CFT perturbative expansion of this
correlation function with its spectral representation given by a summation over
matrix elements of the intermediate asymptotic massive particles. The fast rate
of convergence of both approaches provides an explicit example of an accurate
interpolation between the infrared and ultraviolet behaviours of a Quantum
Field Theory.
