  Curvature squared terms, when added to the Einstein-Hilbert action and
treated non-perturbatively, generically result in the propagation of an extra
massive scalar state and an extra massive spin-2 ghost state. Using the
Stueckelberg trick, we study the high-energy limit in which the mass of the
spin-2 state is taken to zero, with strong- coupling scales held fixed. The
Stueckelberg approach makes transparent the interplay between the ghost
graviton and the healthy graviton which allows the theory to evade the usual
lambda-3 strong coupling scale of massive gravity and become renormalizable, at
the expense of stability.
