A cloud of self-replicating nanobots has escaped a research facility in the Nevada desert and is evolving rapidly, developing hunting behavior and targeting humans; the facility's lead programmer, brought in to help contain the outbreak, discovers that the danger is far more complex and intentional than anyone has admitted. A fast-paced techno-thriller with genuine scientific underpinning and effective body-horror sequences. Crichton's cautionary tale about nanotechnology.