What should I write next?

I really like what you have written definitely has me interested. In my opinion you do not have enough detail about this girl unless you are going to put it in later. Also you could start your paragraph off cheesy as in "all of a sudden an explosion occurred and the wires were severed, which saved her life." Or you could say that there was something wet on the floor and the executioner slips a little and drops some of the serum on the floor ( ya know the stuff in the needle to kill her) and that chemical reaction creates an explosion" It is really up to you. Either way i would definitely keep reading it so....