By Inferno's Light" is the 113th episode of the television series Star Trek: Deep Space Nine, the 15th episode of the fifth season.
Set in the 24th century, the series follows the adventures of the crew of the Starfleet-run space station Deep Space Nine near the planet Bajor, guarding a wormhole that connects the Alpha and Gamma Quadrants of the galaxy, as the Bajorans recover from a decades-long occupation by the imperialistic Cardassians. The Gamma Quadrant is home to a hostile empire known as the Dominion, ruled by the shape-shifting Changelings, whose will is enforced by their ruthless soldiers, the Jem'Hadar, and their administrators, the Vorta. In the middle seasons of the series, the Dominion foments discord between the Cardassians, the Klingon Empire, and the United Federation of Planets.
This episode is the second half of a two-part episode; in its predecessor, "In Purgatory's Shadow", the Dominion prepared to launch its long-awaited invasion of the Alpha Quadrant, as several Deep Space Nine officers and allies were held prisoner in a Dominion detainment facility. This episode sees Cardassia join the Dominion, drastically altering the balance of power in the galaxy. It features the return of several recurring characters and draws on plot lines from the third-season's "Improbable Cause" and "The Die is Cast", the body of the fourth season, and fifth-season opener "Apocalypse Rising".
The episode premiered to almost 6 million viewers.
It is the final episode of the series where any of the main DS9 cast is wearing the original DS9-style uniforms. In this case, the real Dr. Julian Bashir.
