I'm sorry man, but this doesn't really fit in with our guidelines in a philosophical sense. If you would like to know what happens in an overdose, all you need to do is consult wikipedia. Pretty much, you're really high and having a good time and then you die. There's not a hell of a lot of warning besides being very intoxicated. Opioids have a narrow therapeutic window, meaning that a dosage that will provide analgesia is not drastically different from a dose that will kill you.