  In this paper I return to the question of what kind of perturbations on
Alice's side of an Einstein-Rosen bridge can send messages to Bob as he enters
the horizon at the other end. By definition "easy" operators do not activate
messages and "hard" operators do, but there are no clear criteria to identify
the difference between easy and hard. In this paper I argue that the difference
is related to the time evolution of a certain measure of computational
complexity, associated with the stretched horizon of Alice's black hole. The
arguments suggest that the AMPSS commutator argument is more connected with
butterflies than with firewalls.
