where 形容詞子句?

He had a hook where his hand should be.
Literally, it means "he had a hook where (relative adverb = in the place that) his hand should be located".
The implicit meaning is:  he lost his hand which was replaced by a hook instead.
What caused that?
As a result of a fierce sword fight with Peter, he lost his hand and got a hook instead.

where his hand should be---rel. adv cl.to the verb "had"