About 20 years ago I had a four-book series that I read (and let someone from highschool borrow them and never got them back). Each book was about 1 of 4 planets that a person could go to, but could not return because some metaphysical bio-cell changed your body and you would die if you left. Each planet was significant in it's own environment (i.e. one was water based, etc.). In order for this group of government people to get to the planet take care of some issues, they took 4 different inmates from prison, implanted a mind-control device in each of them, and sent them one at a time down to each of the 4 planets. The inmates were controlled by one guy on a space ship orbiting the planets. If anyone read these and happens to know what the titles and author of these four books were, I would appreciate you dropping a note or email (email@example.com) to me. Thanks.