I see the sentence in the book:I don't believe that is who betrayed me..
I can not understand its meaning and I think it is wrong. Am I right?
I see the sentence in the book:I don't believe that is who betrayed me..
I can not understand its meaning and I think it is wrong. Am I right?
The construction is idiomatic and commonplace. It is a short form of saying:
I don't believe that (person) is (the individual) who betrayed me.
In this instance that is being used as a pronoun to refer to the person concerned.
You could insert a second that by saying:
I don't believe that (conjunction) that (pronoun) is (the individual) who betrayed me.
But this is unnecessary. In both spoken and written English, the first that is commonly omitted.
You will frequently come across constructions such as:
I don't believe that's who did it.
I don't believe that's the man responsible.
I don't believe that's who you are.