the Cardassians during the occupation, whom Pallra has been blackmailing. Trazko attempts again to kill Quark; Rom saves Quark's life by screaming, gaining the attention of security officers. Brought to DS9, Pallra denies knowing Trazko, but Odo has confirmed that she recently transferred a large sum of money into his bank account. When she declares her innocence in the murder of her husband, Odo replies, "I know." Odo has realized that it is Kira who killed Vaatrick five years earlier. He tells Kira that he began to suspect her when she was able to identify Ches'saro so quickly. When he deduced that the list consisted of Bajoran collaborators, Odo realized that Vaatrick was a collaborator too, and now understands that Dukat chose him to investigate so as to keep distance from his collaborators. Kira, a member of the resistance, killed Vaatrick when he discovered her trying to steal the list of names. She never told Odo because she was afraid it would affect their friendship. Kira asks him if he will be able to trust her again, and he is unable to answer. Reception When "Necessary Evil" was broadcast in November 1993, it received a Nielsen rating of 9.3 points and 5th place in its time slot. Tor.com rated the episode 10 out of 10, calling it "The perfect DS9 story. Everything that’s great about the show is on display here." It was the only episode of the season to achieve that rating. In 2016, The Hollywood Reporter ranked "Necessary Evil" the 19th best episode in Star Trek: Deep Space Nine. They note this as an episode that differentiated this series from its predecessor, Star Trek: The Next Generation, and place the episode in the murder mystery genre. In 2017, ScreenRant ranked this episode the 11th darkest episode of the Star Trek franchise. In 2018, SyFy recommend this episode for its abbreviated watch guide for the character Kira Nerys. In 2019, Tor.com noted this as an "essential" for the character of Odo, remarking that it helps establish his character and what it was like for him when he worked for the Cardassians. Releases It was released on LaserDisc in Japan on June 6, 1997, as part of the half season collection 2nd Season Vol. 1, which had 7 doubled sided 12" discs. The discs had English and Japanese audio tracks. On April 1, 2003, Season 2 of Star Trek: Deep