One night last week, about 3:30 a.m., I was woken out of a deep sleep by a sound – a sound at once familiar, infuriating, and implacable. I knew instantly what it was, and what I would have to do, and I was already sorry. The sound was indisputably that of gnawing, a sound made by little sharp teeth, carving out a little nest for itself among the studs and cellulose insulation behind our bedroom wall, a sound somehow amplified by the very structure of the wall itself. I should not have been