Talk to Therius and choose 'Yes' (left choice), follow him to the walk way when the castle gets bombed (again).
Zael and Therius will meet up with Count Arganan and Dagran. The party will have to escort Count Arganan to safety.
Arriving at the first open area in the third floor, Gurak troops attack. Defeat them, then head to the second floor.
Attack the next wave of enemies. Ruli knights will come and block off the main entrance, so head to the Courtyard.
The party will be attacked by three Phantom Coffins. Drop them immediately. After that, the party will go through the Military building. Inside the building are a number of Gurak forces, so fight them off and move on. One of the enemies will drop the Healel sword, so grab it and move on. There will be a conversation between Therius and a knight.
The Phantom Coffins return, so kill them as you did before.
Dagran will run ahead of the party. Defeat the Gurak that came out of the lift, and another cut-scene occurs. Zael will go up the lift. In Seek mode, look for the person lying on the ground. Another cut-scene plays.
Another series of unfortunate events occurs, and then move on to Chapter 27.