Hydreigon listens carefully to Adia's words, knocking on the door lightly with his head when she says something he agrees with. He knows something is wrong with his trainer, even if Dark type Pokemon normally enjoy chaos like this, Hydreigon clearly is not supportive of this change. He wants the old Jeff back...

The comment about flying away causes the Pokemon to become upset. He mumbles his name in displeasure to the idea. Nope. He's not leaving Adia or Jeff behind, not after the kindness they showed him as a Deino.
Speaking of bad things happening, Adia might be able to hear the speech that's going on above them. It definitely doesn't sound good, especially after the screaming and shouting starts occurring.