We prove that the group G = Hom(Z N , Z) of all homomorphisms from the Baer-Specker group Z N to the group Z of integer numbers endowed with the topology of pointwise convergence contains no infinite compact subsets. We deduce from this fact that the second Pontryagin dual of G is discrete. As G is non-discrete, it is not reflexive. Since G can be viewed as a closed subgroup of the Tychonoff product Z c of continuum many copies of the integers Z, this provides an example of a group described in the title, thereby answering Problem 11 from [J. Galindo, L. Recorder-Núñez, M. Tkachenko, Reflexivity of prodiscrete topological groups, J. Math. Anal. Appl. 384 (2011), 320-330]. It follows that an inverse limit of finitely generated (torsion-)free discrete abelian groups need not be reflexive.