  We present a new understanding of the unstable ghost-like resonance which
appears in theories such as quadratic gravity and Lee-Wick type theories.
Quantum corrections make this resonance unstable, such that it does not appear
in the asymptotic spectrum. We prove that these theories are unitary to all
orders. Unitarity is satisfied by the inclusion of only cuts from stable states
in the unitarity sum. This removes the need to consider this as a ghost state
in the unitarity sum. However, we often use a narrow-width approximation where
we do include cuts through unstable states, and ignore cuts through the stable
decay products. If we do this with the unstable ghost resonance at one loop, we
get the correct answer only by using a contour which was originally defined by
Lee and Wick. The quantum effects also provide damping in both the Feynman and
the retarded propagators, leading to stability under perturbations.
