Fallout 3 The Waters Of Life quest help?

So, I went to Rivet City after finding out about this Waters Of Life quest, and I went to the science lab in chercher for Doctor Li. I found Doctor Li and asked her about Project Purity, but the quest option never showed up. But then I realized that James was supposed to be there too, so I looked all around the science lab, and James was never there. I also never saw the conversation Doctor Li and James were supposed to have. Is this a glitch; ou do I need to accomplish something first? Help!