Let R=k[T1,…,Tf] be a standard graded polynomial ring over the field k and Ψ be an f×g matrix of linear forms from R , where 1≤g<f. Assume is 0 and that is exactly one short of the maximum possible grade. We resolve , prove that has a g-linear resolution, record explicit formulas for the h -vector and multiplicity of , and prove that if f−g is even, then the ideal Ig(Ψ) is unmixed. Furthermore, if f−g is odd, then we identify an explicit generating set for the unmixed part, Ig(Ψ)unm, of Ig(Ψ), resolve R/Ig(Ψ)unm, and record explicit formulas for the h -vector of R/Ig(Ψ)unm. (The rings R/Ig(Ψ) and R/Ig(Ψ)unm automatically have the same multiplicity.) These results have applications to the study of the blow-up algebras associated to linearly presented grade three Gorenstein ideals.