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Given scene/plot descriptions from movies or TV shows, and given a specific question about the scene, summarize the question into a title

In Fantastic Beasts and Where to Find Them, Newt restrains Graves' movements with one of his friendly beasts and then proceeds to use the Revelio spell to... (spoiler)     reveal Graves' true identity, who is actually Gellert Grindelwald.   My question is, what gave him away? How did Newt realize that man was not really Graves? I was thinking maybe the speech he gave matched...    Grindelwald's ideas   ...and also the power and skill he displayed whilst fighting the aurors. Does anyone have a better explanation for this? Also, as a curiosity, what did...    Grindelwald   ...do with the real Graves? Maybe something similar to what was done to Alastor Moody in The Goblet of Fire?
Output:
How did Newt Scamander realize "someone's" real identity?