ENT Season 1 Episode 26 + Season 2 Episode 1 Shockwave

Plot

Part I

While visiting an alien mining colony on Paraagan II, a shuttle accidentally sets fire to the large amounts of tetrazine in the atmosphere, instantly incinerating the 3,600 colonists on the surface. Despite Lieutenant 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 Enterprise's mission is officially cancelled, and the ship is ordered to return home (on the advice of Vulcan Ambassador Soval).
Later, Archer is suddenly transported back 10 months in the past. He then encounters Crewman Daniels who warns him that the Suliban are trying to sabotage Enterprise's mission. He wants to help Archer discover the truth, because events must go on to preserve the timeline. Using information from Daniels, Reed finds a cloaked Suliban device on the shuttlepod's engine manifold, and Archer directs Commander Tucker to build advanced quantum beacon detectors. 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 still skeptical about the time travel explanation, as Vulcan scientists say time travel 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.

Part II

With 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 gives Daniels his communicator and scanner, allowing Daniels to make a device able to contact Enterprise.
The Suliban take Enterprise to a nearby helix, and 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. 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 the device, to prevent him from using it to get in touch with the Suliban's contact from the future.
Silik then tries to contact his master but he only succeeds in bringing Archer back, Daniels and Archer having managed to set up a device that allows them to return Archer to his time using the communication device as a 'target'. Meanwhile, on 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 their 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 that the Vulcans should learn from their mistakes as well. Soval exits, and it is decided that Enterprise's mission will continue for now.