That is a scary look on his face on page 36.
He is carrying a heavy burden in his heart, obviously Walder didn't say anything with resentment, but in his own grief he forgot his friend last words... but considering what the dragon said about the curse, it isn't really his fault, it is a mental trap, it is already impressive he is alive, much more that he didn't already go mad.
Gaius is made of the stuff of legends.
How must it feel to see members of your race forgetting how to talk?