Sentence:  These <WSD>backstories</WSD> cast the characters' behavior in a new light: of course Gertrude would promptly marry the man who saved her from abuse; of course Ophelia would be desperate and indiscreet in seeking Hamlet's love. 
Meaning of the word marked with <WSD> tags:  The previous life and experiences of a person, especially a character in a dramatic work, but also a real-life person.