"The Child," Star Trek: The Next Generation's second season opener, was based on a story for Star Trek: Phase II. The Writer's Guild strike was going on at the time, so the TNG staff dug out "The Child" and rewrote it for their own characters.
A deadly plague in the Rachelis System ensues, and the Enterprise is assigned to transport plague samples from a Federation research station in order to develop a cure. Meanwhile, Dr. Katherine Pulaski, the ship's new Chief Medical Officer, learns that Deanna Troi has become pregnant.
Deanna reports that she was impregnated by a glowing white light while she slept, and Dr. Pulaski determines that the child will be born within 36 hours. Worf observes the delivery as a security measure, but Deanna gives birth to a harmless baby boy named Ian. The child grows the equivalent of eight years in one day.
Wesley prepares to leave the ship to join his mother, who has become head of Starfleet Medical. But Guinan, a mysterious new bartender, convinces him to follow his heart and stay on board. Captain Picard agrees to let him stay, as long as his mother allows it.
Suddenly, one of the plague containers fails, putting the entire crew at risk. Hester Dealt, a really funny looking guy who sports just a stache and is the doctor supervising the transport, determines that radiation has caused a strain of the plague to start growing. The crew is unable to determine the radiation's source.
Ian realizes that he is the source of the radiation, and he sacrifices his life to save the crew. Deanna is heartbroken, but Ian's body reverts to its white-light state and tells her that he will live on. He explains that he had come to her to learn more about human life, and thanks her for the experience. Troi relates this information to the crew, and the plague containment regains full strength. Ian's life force departs from the ship to parts unknown.