... WTF? I think that's meant to be T'Pol, but she's so heavily made up to be unrecognisable. Confusion.
T'Pol (the usual one) mediatates but is interrupted by Trip who wants more massage porn. She tells him to get lost, but he says he actually came because he's worried about her. She says she's fine.
Enterprise prepares to enter a nebula within which is a subspace corridor to the council. The Xindi, meanwhile, debate some more.
Enterprise is about to enter the nebula when the Enterprise appears behind them. The captain on the other Enterprise asks them to come about. Captain Lorien, a Vulcan, comes aboard and tells Archer that the subspace corridor will send Enterprise back in time a hundred years, which explains where the other Enterprise came from.
Lorien gives Archer designs for modifications to make Enterprise go over warp 6, but Archer is skeptical. Phlox checks them out and confirms that Lorien and her first officer are descended from members of the Enterprise crew. Lorien is the son of Trip and T'Pol.
Trip and Lorien work on modifying the warp engines, and Lorien reveals Trip died. Archer visits the other Enterprise and meets elderly T'Pol. Oh, crap, they need to watch out for the Blinovitch effect.Old!T'Pol gives Archer something for T'Pol.
Reed, Mayweather and Hoshi chat about how their lives turned out, and Reed is disturbed because he didn't have any babies. That's probably because he's ambiguously gay.
T'Pol finds elderly T'Pol has found a flaw in the calculations, and Enterprise can't go over warp 6. However she thinks there's a way to modify the impulse manifolds so they can go through the subspace corridor.
Archer debates the issue with Lorien vaguely, and Lorien then goes and complains to Old!T'Pol. Lorien decides to steal the warp injectors from Enterprise so they can go warp 6 and contact Degra.
Trip chats to T'Pol about their future together. She says the future may not happen that way. Trip walks in on them nicking the plasma injectors and Enterprise 2 attempts to make off. Enterprise 1 knocks out their nacelles. Cue Enterprise dogfight, and T'Pol beams out bits of their power system, disabling them.
Lorien reluctantly surrenders and is chucked in the brig. Archer talks with him some more.
T'Pol visits her elderly counterpart to discuss the modifications to the impulse drive. Old!T'Pol says she'll always have the emotions she's picked up as a result of the Trellium addiction, and she should shag Trip some more.
The Enterprises head into the nebula and heads for the subspace corridor, whacking some Xindi ships in the process. Unfortunately one of the impulse thingees is knocked out, so Enterprise 2 starts towing them with a tractor beam. Enterprise 1 zooms into the subspace corridor and comes back out in the right century.
Five hours later, Lorien's ship still hasn't turned up. Archer thinks that they just retconned the other Enterprise. Degra's ship turns up. Teh end.