Risotto figures out that Doppio must be a Stand user that the boss trusts in deeply because he’s able to hear the noise from a certain Stand. Risotto then uses his Stand Metallic against him. Metallic is able to control magnetic force and attacks Doppio. Doppio uses the part of the boss’s power he received from him. While they’re fighting, Risotto realizes that Doppio’s personality and actions seem to be changing and he realizes exactly who Doppio is.
The iron in your blood 
captures the oxygen
الحديد داخل جسدِك يخزّن الأكسجين
Es ist das Eisen, an dem sich
der Sauerstoff bindet, den du einatmest,
El hierro de la sangre
El hierro de la sangre
Dans tes veines,
Il ferro all'interno del sangue
 cattura l'ossigeno
É o ferro no seu sangue
que captura o oxigênio
Железо ловит кислород,