Keiko O'Brien returns from a botanical trip to Bajor and once alone with Miles claims to be possessed by an entity who requires that O'Brien modify some of the stations systems for a secret purpose. After a couple of frightening demonstrations of the entity's power, Miles is forced to cooperate. Soon however the modifications are noticed, and Odo and Dax start looking for a saboteur.

Rosalind Chao (Keiko O'Brien)
Max Grodénchik (Rom)
Hana Hatae (Molly O'Brien)

• Keiko visited the Cave of the Pah-wraiths on Bajor, and one of them possessed her body. Rom tells us that according to Bajoran legend, Pah-wraiths are the enemies of the Prophets (the wormhole aliens). They make a return in season 6's "The Reckoning".