We prove that the continuum primary field correlations of the doubled massive Ising model in 2D coincide with correlations of a Sine-Gordon model. This is a manifestation of the celebrated correspondence theorized by Sidney Coleman in 1975, at the free fermion point. We independently construct and match correlations on both sides in the case of compactly supported mass, then show that the correlations converge to well-defined quantities under a constant mass limit, which in particular corresponds to the regime where Painlevé transcendent appears in the full plane. Based on a joint work with Christian Webb and Tuomas Virtanen.