Our hero, Professor Andrew Martin, is dead before the book even begins. As it turns out, though, he wasn't a very nice man, as the alien imposter who now occupies his body discovers. Sent to Earth to destroy evidence that Andrew had solved a major mathematical problem, the alien soon finds himself learning more about the professor, his family and "the humans" than he ever expected. When he begins to fall for his own wife and son, who have no idea he's not the real Andrew, he must choose between completing his mission and returning home, or finding a new home, right here on Earth.