  In general, black-hole perturbations are governed by a discrete spectrum of
complex eigen-frequencies (quasi-normal modes). This signals the breakdown of
unitarity. In asymptotically AdS spaces, this is puzzling because the
corresponding CFT is unitary. To address this issue in three dimensions, we
replace the BTZ black hole by a wormhole, following a suggestion by Solodukhin
[hep-th/0406130]. We solve the wave equation for a massive scalar field and
find an equation for the poles of the propagator. This equation yields a rich
spectrum of {\em real} eigen-frequencies. We show that the throat of the
wormhole is $o(e^{-1/G})$, where $G$ is Newton's constant. Thus, the quantum
effects which might produce the wormhole are non-perturbative.
