Klingons and Borg!
Shockwave part two was a great season opener resolving the cliffhanger from the first season.
Marauders is another good story when you learn about the Earth Cargo Service hauling freight aroung the star systems with the crews beings harrassed by the Nausiccan pirates with Enterprise coming to the rescue.
Jean Luc Picard never cleared up the mess he made in First Contact when he destroyed the Borg sphere - the sphere crashed at the pole and the surviving Borg were frozen in the Antartic until discovered by Humans and thawed out and then the nightmare begins!
Camamar is when Archer and Tucker are wrongly mistaken as criminals and fight to survive on a prision ship that has been taken over by the prisioners.
The Expanse is the final episode of the second series when Enterprise is recalled to Earth when the planet is attacked by a mysterious probe.
The Klingons still want Archer and are waiting for him as the crew reach Earth , Enterprise returns to her spacedock and undergoes major upgrades with improved Phase cannons, Photonic torpedos, better armor and a now a complement of MACOs (Marines).
Enterprise is now no longer a ship of exploration - the pride of Starfleet is now a warship and Earths only hope.