“Scorpion, Part II” is episode one of season four of Star Trek: Voyager.
In the season three finale, “Scorpion”, Harry had been hurt badly by Species 8472, but the Doctor had come up with a proposed treatment using Borg nanoprobes. Captain Janeway had suggested they meet with the Borg to discuss an alliance, and they had arrived at a Borg planet to do so. She was onboard a Borg cube when Species 8472 attacked, destroying the planet and a couple of other cubes. The one Janeway was on fled with Voyager in tow.
B’Elanna can’t get a transporter lock on the captain, even though the cube’s shields are offline thanks to being hit by bits of planet. Then the captain hails Voyager and tells them to stop trying. They have come to an agreement with the Collective. Voyager will help design a weapon against Species 8472 in return for safe passage through Borg space. The cube is now heading towards the Alpha Quadrant and they will work on the weapon en route. Once Voyager has crossed Borg territory, they will hand over the nanoprobes. The Borg appear to be holding up their end of the bargain; Voyager needs to do the same. Part of the deal is that Janeway works on the cube. Chakotay asks if the Borg can disengage the tractor beam. Janeway will ask. She also wants Tuvok to transport over.
The Doctor is telling Chakotay how he has progressed in his treatment for Harry, by reprogramming and replicating Borg nanoprobes. He injects Harry, and the treatment works. The Doctor has his doubts about the alliance; a medical treatment is a long way from a weapon of war. Chakotay wants the Doctor to keep all the information on the nanoprobes. The Doctor says he will delete himself at the first sign of trouble. Well, maybe not the first.
Tuvok is now on the Borg cube and the tractor beam is disengaged. In sickbay, Kes sees one of Species 8472 reflected in a console, but there isn’t one behind her. Then she sees one and cowers until the Doctor shakes her. Kes explains that Species 8472 is watching them.
Tuvok and Janeway are being escorted to a work area near the centre of the cube. Tuvok has the analysis of the bioship; the cells share many properties with those of the aliens. The ships and the aliens are made of the same tissue. Janeway explains to the Collective about the modified nanoprobes and that they need a large-scale delivery system. First, though, the Collective wants to fit them with neurotransceivers. Janeway and Tuvok protest that they work better with their individuality intact. And they will not help if implanted, even if only temporarily. Instead, Janeway suggests the Borg designate a representative, like Locutus, to work with. A drone, definitely female, is activated, and she says she, as in ‘I’, speaks for the Borg. Pronouns are highly unusual with the Borg.
The drone’s designation is Seven of Nine, Tertiary Adjunct of Unimatrix Zero One. But they can call her Seven of Nine. She considers the use of photon torpedoes to distribute the nanoprobes to be inefficient. Janeway asks if she has a better idea. ‘We are Borg’ is the answer. Tuvok takes that as a yes. The Collective’s suggestion is to use a weapon big enough to affect an entire star system and distribute the probes over 5 light years. It’s efficient. Tuvok states it will take too long and the Borg are losing. The enemy thinks they are invulnerable. A few smaller weapons would disabuse them of that. Seven of Nine gives an insulting answer, but the Borg will consider it. They have information on Voyager‘s torpedoes. How? We are Borg.
On Voyager, the Doctor is scanning Kes when Chakotay arrives. He feels that the visions are more than a simple hello. On the cube, Janeway says to Seven of Nine that she’s human. She was assimilated 18 years ago and ceased to be human at that time. Voyager hails them and it’s explained about Kes and that Species 8472 may know what they are doing. Seven of Nine states they need to construct a test prototype now.
Harry has recovered and returns to the bridge. Then a singularity opens behind Voyager and a bioship comes out. The ship attacks Voyager, but the cube intervenes. The cube’s weapons do nothing, but it interposes itself and then crashes into the bioship, destroying both. Tuvok contacts them from cargo bay 2; he, Janeway and several Borg were beamed aboard.
The Borg are already assimilating the cargo bay when Chakotay and a security team arrive. Seven of Nine state they are there with the captain’s consent; it was necessary to sacrifice the cube to protect Voyager. They have an alliance, do they not?
Janeway was badly injured during the attack and the Doctor is going to put her into a coma. That leaves Chakotay in command, and Janeway has asked him to make an alliance he didn’t want in the first place work. The Borg are rapidly losing the war and Voyager is deep within Borg space.