The planet where the elderly Admiral Mark Jameson and his wife Anne were living in 2364 when the Enterprise collected him to negotiate a hostage crisis on Mordan IV.
Persephone V appears at the start of the Next Generation episode Too Short a Season. When Governor Karnas of Mordan IV reports that terrorists have seized the Federation ambassador and insists on dealing with Jameson, who resolved a similar crisis there decades before, the Enterprise is sent to fetch him.
Jameson, in his eighties and confined to a support chair by Iverson's disease, comes aboard with Anne. Unknown to Starfleet he has been taking an alien rejuvenation drug obtained on Cerberus II, and he swallows the whole remaining supply for the mission.
He grows visibly younger during the voyage, but the overdose is killing him. He dies on Mordan IV after facing Karnas, who had invented the hostage story for revenge.