"Shockwave" is a two-part episode and of the television seriesStar Trek: Enterprise. Part one is the first season finale, the twenty-sixth episode (production #126), and part two is the second season opener, the twenty-seventh episode (production #128).
While visiting an alien mining colony on Paraagan II, an Enterprise shuttle accidentally sets fire to the large amounts of tetrazine in the atmosphere, instantly incinerating the 3,600 colonists on the surface. Despite Lt. Reed's precautions, Captain Archer personally puts full blame on himself for all the deaths caused. He doesn't argue with Starfleet's Admiral Forrest when the Enterprise's mission is officially cancelled, and the ship is ordered to return home (on the advice of Vulcan Ambassador Soval).
When Archer goes to bed, he is suddenly transported back 10 months in the past. He then encounters Crewman Daniels who had brought him back in time to warn him that the Suliban are trying to sabotage Enterprise's mission. He wants to help Archer discover the truth, because the Enterprise's mission must go on to preserve the timeline. Using information from Daniels, Reed finds a cloaked Suliban device on the shuttlepod's engine manifold. They then proceed to check the specifications of a Suliban cloaked ship in a database in Daniels's quarters. Archer directs Commander Tucker to build advanced quantum beacons to detect Suliban ships while cloaked. Enterprise then travels back to an asteroid field near Paraagan II where a Suliban ship is hiding. They quickly cripple and board the ship, finding computer memory chips with proof of the Suliban's plan.
As Enterprise makes its escape, they are able to prove that the explosion wasn't their fault. Sub-commander T'Pol is, however, still sceptical about the time travel explanation, as Vulcan scientists have proved it is impossible. Later the ship starts experiencing warp field problems, and soon detects 20 or 30 Suliban cell ships in pursuit. The ships decloak, and Silik orders Archer to surrender himself. Archer puts T'Pol in command, but he never makes it to the Suliban shuttle, as he is time transported again, this time to a derelict 31st century building overlooking a devastated cityscape. Daniels appears behind him telling him that bringing him into the future to protect him caused this dramatic change in the timeline. Archer asks to be sent back to repair the damage, but since all the time travel equipment is gone, they are both trapped.
With Captain Archer gone, T'Pol chooses to surrender the ship to the Suliban to let them verify his disappearance. They do not find any trace of Archer, but they retrieve their data disks and detect a temporal signature in the turbolift. Meanwhile, in the 31st century, Daniels realizes that there is no available technology to send Archer back and, because of this, the timeline has been disrupted. Archer however gives Daniels his communicator and scanner, allowing Daniels to make a device able to contact Enterprise.
The Suliban confine the crew to quarters and take Enterprise to a nearby helix. Silik interrogates T'Pol to learn where Archer has gone, but she knows little. When T'Pol is returned to her quarters, Archer contacts her and gives her instructions on how to bring him back. Meanwhile Tucker is able to set up a communication link between the senior staff, and they plan an escape. Ensign Sato, the only one small enough to crawl through the air vents, is able to reach to Dr. Phlox, who has prepared some hyposprays to disable the guards, and then makes her way to Reed's room. The plan begins when two Suliban find T'Pol acting strangely, and are knocked out by Reed and Ensign Mayweather.
Reed then goes to Daniels's quarters to retrieve a futuristic device, but is caught by the Suliban. During interrogation, he tells Silik that Archer gave him orders to destroy it, to prevent him from contacting someone, most likely the Suliban's contact from the future (a deception). Silik then returns to the helix and tries to contact his master but he only succeeds in bringing Archer back. Meanwhile on the Enterprise, a faked warp core breach is initiated, forcing the Suliban to evacuate the ship. As soon as they are freed, Enterprise goes to warp, pursued by Suliban ships. Archer destroys Daniels's device and, having taken Silik hostage, secures the Enterprise's escape.
The reunited crew finally present their proof to Starfleet Command and the Vulcans. Soval still recommends cancellation of the mission, but Archer promises that humanity will learn from their mistakes. T'Pol supports him, adding ideas about the Vulcans' need to learn from their mistakes as well. Soval exits, and it is decided that Enterprise's mission will continue for now. Archer thanks T'Pol for her support.