So you first have to do everything and I mean it, includes visiting all the locations, robbing the store, beating up the homeless dude, etc. After that you go to the dark street and talk to the man who sells the "good stuff" and buy it from him, then push the wall and find the secret door but do not enter, go back and go to morshu's shop then go to act, talk, and then you should see an option saying "Tell him a secret..." if it does not say this you more likely than not missed something, and then BOOM you just got it. :D