In the second half of the twenty-first century, the U.S. Robots & Mechanical Men Corporation places on the market first, perfect models of positronic robots, capable of also replace humans in jobs delicate. The new steel allies of the human race are the police, the servants and even the baby sitter. I'm pretty sure: in fact, thanks to the three laws that govern their programming, they can not become criminals or impair in any way to their employers. But is this true? Every so often unlikely event occurs, every time a robot gives warning signs of imbalance ... It is at this point that the "case" passed into the hands of Susan Calvin, the robopsicologia of U.S. Robots. She knows that the new models and best of all is that you can avoid the risk of more serious consequences. But sometimes their work is not so easy ...
