Martin has a 10 hour window of opportunity to make it home since Mars has deviated from its regular orbit temporarily and is closer to Earth than usual. Just as he is about to leave, he slips down the stairs and sprains his ankle and disappearing antenna. Mrs. Brown immediately calls an ambulance. They rush him to the hospital since his vital signs aren't "human". Martin does all he can to have normal human vital signs. He passes that test, but when the doctor requires a fluoroscope, Martin is worried since the gamma rays from it will make him explode. Tim manages to take the fluoroscope for Martin, but the doctors keep Martin to figure out why the scan shows he has the body of a 20-year-old. With one hour to spare, Martin regains the use of his disappearing antenna and escapes from the hospital. Just as he is ready to leave for the second time, Martin slips down the stairs again and sprains his other ankle. Nothing can help him this time and he misses his opportunity to get home. (thetvdb.com)