contract our brow in consternation
Sorry if this assumes too little knowledge of English.
frown = wrinkle your brow in thought or disapproval
brow = forehead or eyebrows
eyebrows = the hairs above your eyes , usually separate but sometimes one.
consternation = great surprise and anxiety ; or dismay
So the sentence is describing the brow moving due to emotion.
a look of dismay showed by the movement of his forehead. ( a very clumsy sentence so please forgive me)