After 2 years in space, a satellite is returned to earth and is found to have a mysterious substance on its outside surface. Tamara is called in to help in the investigation until Keith Mason and his team from Ames Research push her aside and exclude her from valuable information. Tamara has, however, reserved a sample and does her own research, enlisting D.B.'s help, and discovers that amazingly enough, the substance contains living cells. Mason finds out what she has done and takes steps to bar her completely from further involvement. For the first time Tamara begins to realize that there is more going on than she ever suspected and realizes that she will likely never find out the truth behind what she has found. Meanwhile, while preparing for his first Shuttle mission, Reggie makes the (well-intentioned) mistake of allowing a friend to sleep at his place for a few days. The distraction of a loud houseguest and the stress caused by lack of sleep have him making careless mistakes, while training, which could cost him the mission that he has dreamed of for so long. Also, Barbara - hoping to get full medical clearance to resume her ASCAN training - has Riles doubting her abilities after an episode during a training flight.