  I discuss features required for preserving unitarity in black hole decay and
concepts underlying such a perspective. Unitarity requires that correlations
extend on the scale of the horizon. I show, in a toy model inspired by string
theories, that such correlations can indeed arise. The model suggests that,
after a time of order 4M ln M following the onset of Hawking radiation, quantum
effects could maintain throughout the decay a collapsing star within a Planck
distance of its Schwarzschild radius. In this way information loss would be
avoided. The concept of black hole ``complementarity'', which could reconcile
these macroscopic departures from classical physics with the equivalence
principle, is interpreted in terms of weak values of quantum operators.
