After an alien probe kills millions on Earth, Archer leads a refitted Enterprise into the Delphic Expanse to find those responsible.
An alien probe attacks Earth, carving a path of destruction from Florida to Venezuela and killing millions, including Tucker's sister. The Suliban's mysterious future contact tells Archer that the Xindi built the weapon and are planning a larger one to destroy Earth.
Starfleet refits Enterprise and adds a team of military specialists called MACOs, then sends it into the Delphic Expanse, a hazardous region of space. T'Pol resigns from the Vulcan High Command so she can stay with the ship. The second-season finale was directed by Allan Kroeker and written by Rick Berman and Brannon Braga.