What would be the most appropriate expression (idiom or phrase) to describe a situation where one person, usually innocent but related to the other person in some way, becomes the unfortunate target of some sinister plot aimed at the other person?
Movies abound in such tropes where A, usually the polar opposite of B, for no fault of his has to bear the brunt of B's underhanded dealings, the cost borne more often than not being a very high one— A loses his life; B avenges his death afterwards, and all that jazz.
Just to make it a bit more clear, targetting A is seldom the intent of the party who murder him. He gets murdered mostly because of a misconception or some such factor that suddenly supervenes as if to save A.
Please note that whipping guy, scapegoat, Aunt Sally, and other such words— these ain't what I'm looking for. I have also already ruled out collateral damage lest anyone should be tempted to post this one as answer, for obvious reasons.
I hope I've made myself sufficiently clear.