The conflict in Rappiccini's Daughter is that Giovanni Guasconti watched Beatrice through his window, but never talked to her until after he was told a story of a poisonous girl
The theme of the story is that even the nicest things in life can kill you. This is explained by when Giovanni gives Beatrice the antidote to try and cure her, but actually kills her in the end.
The fountain is a symbol of Beatrice because you are taught not to touch the fountains or the water. In the book, Beatrice cannot touch things because she is poisonous and will harm whatever she touches.