The Husband kept grousing about how this show has jumped the shark by bringing in Grand Moff Tarkin and Darth Vader. In actuality, their presence serves as an entre'acte to move the team of the Ghost from Lothal to the Rebel Fleet.
After busting Kanan out of the clutches of the Empire, the Ghost crew repays the Rebels by trying to secure a cargo of military-grade forcefield generators from an Imperial cargo convoy. They succeed in liberating the cargo, but the generators are not part of it.
Kanan is chafing under the military hierarchy of the Rebel fleet, and wants to go back to being an independent operator. His crew receives a call from one of their Lothal contacts, who puts them in touch with Minister Tua, the regional Imperial representative on Lothal. After failing to capture the Rebel cell on her planet, Minister Tua believes her life is in danger from Governor Tarkin, and is asking to be rescued in exchange for some secret Imperial information useful to the Rebel cause. While most of the Ghost crew feels it's a trap, Ezra feels that the Minister really is sincere, and frightened. He talks the others into a rescue mission.
However, their effort goes horribly awry when Agent Kallus boobytraps the Minister's shuttle, killing her, and framing the Rebels for it. Now they need to smuggle themselves off Lothal.
They appeal to Lando Calrissian, who agrees to make available some materials to them--in exchange for three of the six shield generators they managed to steal while attempting to rescue Minister Tua.
They succeed in escaping the planet, but there is a tracking device in their ship (why don't they think to scan for these things--I mean, they hijacked an IMPERIAL SHUTTLE for cryin' out loud!) and they lead Darth Vader straight to the Rebel fleet.
Ahsoka Tano, a carryover from the Clone Wars series, senses the presence of her old mentor Annakin Skywalker, but does not reveal this to Kanan, who only knows that a very angry Sith Lord is after them. The fleet attempts to engage Vader, resulting in the loss of their command ship. Deciding that a tactical retreat is in order, the fleet jumps to hyperspace while the Ghost gives them covering fire, itself escaping from between two Star Destroyers just as they engage their tractor beams--catching Darth Vader's TIE fighter between them.
The crew of the Ghost decide that, for the good of Lothal, they cannot return there, and vote to join the Rebel Fleet.