"The Expanse" assembles a mystery and a cliffhanger to predictably end the second season of Enterprise. An automated weapon which Archer believes to be a Xindi probe enters Earth-space and cuts a swath from Florida to Venezuela,killing millions. Archer is contacted by an emissary from the future and told that an invasion is being prepared in the Delphic Expanse - a region of space which the Vulcans, and seemingly everybody else, are terrified of. Meanwhile, the Klingon fugitive subplot is kept alive as Enterprise is pursued by Klingon Birds of Prey (this is really just added to provide some additional action in an otherwise sedate episode, since it has no bearing on the central plot), and Enterprise is refitted with better hull plating and antimatter torpedoes (completely scientifically absurd, but the franchise hasn't really been very concerned with science since DS9 so who cares).
The acting is a touch above the average for this series. The script allows Conner Trinnear to capitalize on American emotions surrounding the 9/11 attack on the U.S.A., as he turns in one of his finest performances during this series. Jolene Blalock also does a very nice job with one of T'Pol's more complicated early interpretations (this character has one of the best arcs in the series, and becomes much more interesting in the 3rd and 4th seasons). However, the script does not just follow franchise formulae, but almost plagiarizes the film Event Horizon in its exposition on the Delphic Expanse.
Entirely predictable, but worth watching because it sets up a good Season 3 opener "The Xindi", and an excellent story arc within the expanse itself.