What changes from the original story is Leo begins to get suspicious quicker than normal of Ariet. He witnesses more of the other people of the panel going about their daily activities and questions more of them as he sees more and more; and includes witnessing and connecting their borderline cult behavior centered around Ariet in his mind.
continuation under cut
I'd like to think one night Leo ended up sneaking out of his quarters without anyone's knowledge due to his suspicions. He would go into one of the little 'labs' and would snoop around and eventually find the databases of the other subjects, including a file named "Subject 003" that's blank, signaling they haven't created it yet. So he's on edge now, expecting to be double crossed at any point now. Either to be used for this little project of theirs, or anything related to it.
Once the golden moment comes where Ariet coaxes Leo into the room where he originally gets strapped down and injected, he wears a completely fake mask of aloofness in the situation like he knows nothing. Once they enter the room and Ariet goes to grab him, Leo immediately pushes him away and knocks him against the exam table. Two other panel members, acting as guards try going for Leo now. Though before doing so, Leo grabs the nearest object, a needle with the substance that 'turns' people the subjects into who they are.
The thing is, with the guards, they can't have Leo killed, they can't do anything with someone who's dead, so they just stare at him before Leo stabs Ariet in the neck.
The people of the panel see Ariet almost as a god, so they worry about him more than anything and him possibly getting hurt, so that's the point where one tackles him and the other goes immediately to Ariet's aid, but! The deed is done and there's zero reversing it once it's in your system, which is one of the major flaws of this substance, it's permanent and untreatable to get back to your older self.
The guards, both stunned and furious, put Leo into a cell as they have more members of the Panel deal with Ariet. Ariet at this point though is completely unconscious, so they put him in a separate cell for monitoring, one they specifically use for the subjects when they start to turn.
Eventually, as the day goes on, bro is completely gone! As in his human self, of course. He's now the new Subject 003, his plans failing and turning on him completely with the fact that Leo is supposed to be in the position he's in now.
The Panel, is honestly just... very discombobulated after this happens. They have and yet haven't lost their leader. At the same time though, The Panel's job is to house, monitor, and train the subjects in whatever ways they need. So, they're all split, either needing to treat him as a test subject, or their leader.
Some others though have begun to see Leo as a replacement for their leader being turned into a subject, for the bravery and sheer force of will to be able to do such a thing, and to do it successfully.
