Cold Lazarus (S01E06)

On planet P3X-562, the SG-1 team discovers a valley full of broken crystals. Alone, Col. Jack O'Neill finds an intact crystal, from which blue light emanates. Upon touching it, he is struck down and a duplicate O'Neill appears. The double returns home through the stargate, with the unsuspecting SG-1 team. Once on Earth, the double seeks out O'Neill's estranged wife, Sara, and tries to find the couple's son, Charlie, who was killed years earlier. Meanwhile, a revived O'Neill returns through the stargate, only to realize that he's been replicated. Capt. Samantha Carter and Dr. Daniel Jackson have discovered that the crystals contain energy beings that can read minds, mimic people, and communicate. The beings tell of their tragic encounter with the Goa'uld and explain that they cannot survive in Earth's intense electromagnetic field, which means that the O'Neill double is now highly unstable, putting Sara and others in great danger. The real O'Neill and the SG-1 team find Sara and the double in a hospital emergency room. The double explains that he never meant to hurt O'Neill. He was trying to heal him when he realized that the greatest pain O'Neill had was not physical, but emotional: grief from the loss of his son. In a final gesture, the double does just that, taking the form of Charlie and giving Sara and Jack something they never had: a chance to say good-bye to their son. (Metro-Goldwyn-Mayer (MGM))