“Zero Hour” is episode twenty-four of season three of Star Trek: Enterprise and the season finale.
Dolim is leading a toast to the future where the Reptilians take their rightful place at the head of the new Xindi empire.
In the previous episode, “Countdown”, Captain Archer took Degra’s ship in pursuit of the Xindi weapon. The Primate reports to Archer that the Reptilians are 3 hours ahead but they’re faster and closing the gap. Reed points out they aren’t well armed. They also can’t tell how many ships are escorting the weapon. The captain says they can only destroy the weapon from the inside anyway. Jannar isn’t getting anywhere with Degra’s encryption of the schematics. The captain says they need Hoshi’s help. They have no choice. He asks Jannar to transfer the schematics to a PADD or something.
The Sphere Builders are concerned. Favourable timelines are still diminishing and Enterprise is on course to the primary Sphere. The transformation of space around that Sphere needs accelerating.
T’Pol checks with Trip to see how he’s doing. He’s concerned that he’ll fry every system onboard. T’Pol gives him two hours. Trip doesn’t want to destroy the ship. T’Pol tells him that without humanity the Expanse will grow, encompassing system after system. Including Vulcan. His world is no longer the only one in jeopardy. When she arrives on the bridge, Travis tells her there’s a problem. He can pick up the Sphere and they shouldn’t be able to. What he’s detecting is getting bigger. It could be spatial anomalies.
In sickbay, Phlox confirms it. Space is being transformed, not unlike that found in “Harbinger”. T’Pol says they need to get within a kilometre of the Sphere. Phlox says the entire crew will be dead minutes after entering the region. He can create a compound to help, but not stop the epidermal decay.
The captain is with Hoshi who is not doing so well. She’s losing track of what she’s doing and where she is, then feeling guilty about getting the final code. The captain encourages her. She needs to complete the decryption; everything hinges on it.
Dolim is told the weapon will come out 2 million kilometres from Earth. As they don’t have all five firing codes, they need more time to activate the weapon and it will be vulnerable closer to the target.
Travis enters engineering. Trip has found a way not to blow the ship up. But he needs power from the impulse engines. Travis will need to approach the Sphere on thrusters only.
Reed is saying they can’t transport to the control platform of the weapon; it’s too well-shielded. The Primate asks what if they have to board before Hoshi has finished her decryptions. The captain is taking her with them. Jannar asks what makes him think he can get out in time. The captain has no plans to die there. He leaves the bridge.
And arrives somewhere and somewhen else, courtesy of Daniels. The future, a little more than seven years from now. The day that Captain Archer, and the Vulcans, Andorians and Tellarites, sign the charter for the Federation. If the captain is killed, it will not happen the way it’s supposed to happen. It’s essential he be a part. And someone else. The captain thinks it’s essential that Earth be there as well.
Phlox is making a recording to distribute his possessions on death when T’Pol enters sickbay. He has the medication. Travis contacts T’Pol; they’re approaching the coordinates. Travis says the region is larger; it’s expanded by 100,000 km. Phlox’s medication will last for 15 minutes.
Hoshi has made progress; she’s found the sequence needed but not decrypted it yet. On the bridge, the captain is told the Insectoid ship isn’t with the weapon. They don’t know Dolim blew it away.
Dolim is told Degra’s ship is 20 minutes behind them. It’s no better armed, though. Dolim informs the Reptilians on the weapon they’re about to emerge. Dolim himself is told there are no Earth ships near the coordinates, only a single unarmed station.
Degra’s ship emerges as well; Dolim is heading towards the station. Enterprise is approaching the Sphere and Trip says something is happening to his skin. Phlox says it’s expected; try not to scratch it. Dolim decides to get a head start on wiping out humanity band blows away the station.
Despite everything, things are still not going the way the Sphere Builders want. They decide to intervene directly. The battle takes place on three fronts; by the Sphere, near the weapon and inside the weapon itself.
The episode ends on a cliff-hanger leading into season four and “Storm Front”. A truly bizarre cliff-hanger, which led to speculation that the creators either wanted to make things difficult for the new ones taking over, or that because there was a definite fear of cancellation, they wanted to ensure the network got a significant backlash if it was cancelled.