SG-1 visits a new planet, one where machinery has replaced people. Before they can withdraw, they are knocked unconscious and awaken wearing different uniforms, but otherwise seem all right. When they do meet their host, Harlan, he is somewhat circumspect about what may have happened to them. They return to Earth, despite Harlan's protestations, but Dr. Fraiser's medical exam reveals they are no longer flesh and bone - it appears their their consciousness has been transferred to android bodies. As they weaken, they realize they must return to the planet as it is the source of energy for their new mechanical bodies. On return however, they are told that their bodies may have been destroyed. It's not quite that simple however.
—garykmcd