Physics knows three dimensions of space - length, width and height. However, there is another dimension, the exploration of which can be quite exciting and incredibly dangerous. And this dimension is time. In the story “Prisoners of Duty,” Doctor Pavlysh finds himself on a planet where four scientists are studying time as a physical quantity. The story was not published during the author's lifetime. This is the final book in the series about Doctor Pavlysh, a Far Fleet cosmonaut. The book also includes the stories “Half a Life,” “Cinderella,” and “A Law for the Dragon.” The publication is supplemented with black and white illustrations by Victor Mineev.