  We propose a four-dimensional supersymmetric theory that deconstructs, in a
particular limit, the six-dimensional $(2,0)$ theory of type $D_k$. This 4d
theory is defined by a necklace quiver with alternating gauge nodes
$\mathrm{O}(2k)$ and $\mathrm{Sp}(k)$. We test this proposal by comparing the
6d half-BPS index to the Higgs branch Hilbert series of the 4d theory. In the
process, we overcome several technical difficulties, such as Hilbert series
calculations for non-complete intersections, and the choice of $\mathrm{O}$
versus $\mathrm{SO}$ gauge groups. Consistently, the result matches the Coulomb
branch formula for the mirror theory upon reduction to 3d.
