ok I think I get what's happening: Cain wanted to find the doctor because he would be able to heal cain from that magic that's threatening his heart, so cain ordered sid (his right hand man, the guy with the red magic) to find the doctor with the compass he has been given. But for some reason sid doesn't want cain to heal, so he goes behind his back and ordered for the other guy to go find the doctor with the compass and then kill him. That's what the other guy did, not knowing that who he decapitated was merely a clone from the actual doctor.
Now, the doctor came to seek a deal with cain, but now that sid is here he cant reveal his identity because if he does say he is that specific doctor that cain has been searching for and doesnt have proof and sid claims that the actual doctor is dead already, the doc would be killed easily because cain trusts sid more than him. So now the doctor is trying to find a way to prove his abilities without getting killed, and sid is planning to get rid of him once and for all, now that he knows that the clone that was killed was not the actual doc
Sorry if this is confusing lol, english isnt my first language 
also your english is perfectly good!
