On Wednesday, there was no sign of business at Dell's, whose modern machinery was silent and whose employee door was closed. Investigators were entering the factory and leaving with boxes of evidence as wind blew in off the iced-in shores of the nearby Buttermilk Channel. Feral cats and a few dog walkers wandered through the quiet neighborhood, which is far from any subway line and a mix of industrial warehouses, single-family homes and small businesses.