Scorpion

"Scorpion" is a two-part episode of Star Trek: Voyager, the cliffhanger between the third and fourth seasons composed of the 26th episode of the third season and the first episode of the fourth. It introduces the Borg drone Seven of Nine and Species 8472 to the series. In this episode, the Federation starship Voyager makes a "pact with the devil" in order to combat a new enemy which poses a serious threat to both.