Sorry this is late--I was rather busy getting ready for a family Thanksgiving week visit, and only just watched this last night. While it had more action in it, the actual plot advancement was kind of negligible.
The crew of the Ghost is trying to protect Ezra's family friend, Tseebo, from being captured by the Empire. Hera intends to hand Tseebo over to her mysterious contact, Fulcrum, so that the Rebellion can exploit the Imperial specs that Tseebo had uploaded into his cybernetic brain implant. Unfortunately, the sheer volume of information has left Tseebo mentally crippled, and unable to give Ezra a straight answer about the fate of Ezra's parents.
The Inquisitor has managed to attach a tracking device to the rebels' ship and is pursuing them through hyperspace. Fortunately the beacon is locked onto the Phantom, which is the Ghost's shuttle, so Kanan decides to detach from the Ghost in order to throw the Inquisitor's fleet off their trail. He takes Ezra with him, for the Inquisitor could still sense the Jedi on board and the whole point is to give Hera a chance to hand Tseebo over to Fulcrum.
Detaching in hyperspace is dangerous, apparently, and chews up several minutes of special effects time, but the Phantom survives it, and lands on the same asteroid where Hera and Sabine had fought with the daylight-hating Fyrnocks. As expected, the Inquisitor follows the shuttle down. He anticipates an easy victory, but in the meantime, Ezra and Kanan use the Force to control the Fyrnocks and send them against the Imperials.
The Inquisitor is still a badass opponent, and he manages to reach and engage Kanan. He knocks Kanan unconscious, then goes for Ezra, who channels his fear and summons up the Mother Of All Fyrnocks, which proves to be a formidable obstacle to the Inquisitor. While it keeps the villain busy, Ezra grabs Kanan and returns to their ship, where they manage an escape, destroying the Inquisitor's ship on their way out.
Somewhere else in the galaxy, Hera has docked with a Rebel blockade runner and turns Tseebo over to Fulcrum. Tseebo, whose mind has cleared somewhat, reveals to her the fate of Ezra's parents, but Ezra is in no condition to hear this when he and Kanan return, for in summoning the giant Fyrnock, he had left himself open to the Dark Side of the Force, and is not well. Kanan is concerned about how fast Ezra's abilities are advancing--almost faster than Kanan is prepared to guide.
Sabine tries to cheer Ezra up by showing him a holodisk from his abandoned family home, with a picture of his parents on it.