  We extend the form-factors approach to the quantum Ising model at finite
temperature. The two point function of the energy is obtained in closed form,
while the two point function of the spin is written as a Fredholm determinant.
Using the approach of \Korbook, we obtain, starting directly from the continuum
formulation, a set of six differential equations satisfied by this two point
function. Four of these equations involve only spacetime derivatives, of which
three are equivalent to the equations obtained earlier in \mccoy,\perk. In
addition, we obtain two new equations involving a temperature derivative. Some
of these results are generalized to the Ising model on the half line with a
magnetic field at the origin.
