Sub Rosa

Beverly travels to Caldos IV to attend the funeral of her grandmother, Felisa Howard. At the service, Beverly sees a strange young man toss a camellia — Felisa's favorite flower — into the grave and give Beverly a knowing look. Beverly then returns to Felisa's house, and is interrupted by Ned Quint, who has been taking care of the place for five years. Ned insists Beverly throw out a candle that has been in her family for generations, claiming it has brought the Howard women bad luck, but she refuses. Back on the U.S.S. Enterprise, Geordi and Data learn that there has been a power fluctuation in Caldos IV's weather control system, while Beverly reads in her grandmother's journals that Felisa had a young lover named Ronin. That night, Beverly experiences strangely pleasant sensations while sleeping, then is awakened by a man's voice, but finds no one there.

The next day, Beverly visits Felisa's grave, where she again encounters Ned. He tells her Felisa's house is haunted and warns her not to light the candle — it will bring the ghost he believes is responsible for Felisa's death. He leaves, and Beverly notices her grandmother's grave has suddenly been covered with camellias. A severe storm then hits, and Beverly runs inside Felisa's house. She is shocked to see that it has also been filled with camellias.

While searching the house, Beverly hears the man's voice from before. He identifies himself as Ronin, a ghost that has loved the women in Beverly's family for eight hundred years. Ronin tells Beverly he loves her, then she feels the strangely pleasant caresses again, but she somehow finds the composure to ask him to stop. Meanwhile, the power transfer that Data engaged with the planet's weather control cannot be cut off, and is now affecting weather on the Enterprise. Data and Geordi soon discover why — Ned Quint is tearing at a power conduit on the planet's surface, shouting that "he'll kill us all!" Suddenly, a flash of green plasma energy leaps out of the conduit and kills Quint.

Beverly scans Quint's body and discovers that something other than the plasma discharge killed him. She then returns to Felisa's house to see Ronin, who tells Beverly that she can keep him in corporeal form by lighting the candle — something the women in her family have done throughout the centuries. Beverly returns to the Enterprise and lights the candle. Ronin appears, telling her that he can now become part of her forever. Later, Beverly abruptly resigns her post on the Enterprise to remain on Caldos IV and become a healer, like Felisa.

Data informs Picard that energy similar to that which killed Quint is coming from the cemetery. Later, Ronin returns with Beverly to Felisa's house, only to be interrupted by Picard, who questions Ronin about his origins. Data then asks Picard's permission to exhume Felisa's body. This sends Ronin into a panic, and he blasts Picard with green plasma energy. At the gravesite, Felisa's body comes to life, enveloping Data and Geordi with another burst of energy. Beverly arrives, recognizing this is Ronin, and tells him to stop. She then realizes he is not a ghost, but an anaphasic lifeform that has been using the women in her family to stay alive. He asks her again to stay with him, but she destroys the candle and then blasts Ronin with her phaser, killing her "dream lover" forever.