An ageing admiral who used an alien drug to make himself young again so he could return to the planet where he had once made a terrible mistake.
Admiral Mark Jameson was ill with Iverson's disease when he came aboard the Enterprise-D with his wife, Anne, in Too Short a Season. He had been asked to negotiate the release of hostages on Mordan IV, where decades earlier he had ended a hostage crisis by secretly arming both sides, which led to a long war.
On the way, Jameson used an overdose of an alien drug that reversed his ageing. The hostage-taker was Karnas, the planet's governor, who wanted revenge on him. Jameson's younger body began failing from the drug, and he died after Karnas finally released the hostages.