Penumbra (Star Trek: Deep Space Nine)

"Penumbra" is the 167th episode of the television series Star Trek: Deep Space Nine, the 17th episode of the seventh season. It aired on syndicated television the week of April 5, 1999.

Set in the 24th century, the series follows the adventures of the crew of the Starfleet-managed space station Deep Space Nine near the planet Bajor, as the Bajorans recover from a decades-long occupation by the imperialistic Cardassians. The station is adjacent to a wormhole connecting Bajor to the distant Gamma Quadrant; the wormhole is home to powerful alien beings worshipped by the Bajorans as the godlike "Prophets", who have made Deep Space Nine's human captain Benjamin Sisko their "Emissary". The later seasons of the series follow a war between the United Federation of Planets and the Dominion, an expansionist empire from the Gamma Quadrant ruled by the shapeshifting Changelings, which has already absorbed Cardassia.

This episode begins the nine-episode concluding story arc of the series, which brings the Dominion War and other story elements to a close. In this episode, Lt. Cmdr. Worf is missing in action after his ship is attacked by the Dominion, and Lt. Ezri Dax goes in search of him; both end up captured by enigmatic aliens known as the Breen. Ezri is a member of the Trill species, symbiotically joined to the long-lived sluglike creature Dax; the previous host of Dax was Worf's late wife Jadzia, and the complex fact of Ezri's existence leads to complicated feelings between her and Worf.