Jane saves Mr. Rochester’s life by pouring water on him when he was on fire.
Jane discovers that Mr. Rochester’s bed has been set on fire, so she pours water on him.
The hiss of the quenched element, the breakage of a pitcher which I flung from my hand when I had emptied it, and, above all, the splash of the shower-bath I had liberally bestowed, roused Mr. Rochester at last. (ch 15)
The fact that he asks her if there is a flood indicates how soundly asleep he was. He is shocked to wake up in a pool of water, and has no idea that there has been a fire. He asks her if she plotted to drown him and she responded, “…Somebody has plotted something: you cannot too soon find out who and what it is." (ch 15). This demonstrates his confusion and her quick thinking. If she had not realized what was happening he would have died.
Mr. Rochester’s first wife is not in her right mind. She still does not like being locked up, though he can’t bear to let her go. He feels responsible. She tries to kill him and Mr. Rochester still does not let Jane in on the whole story. He asks her what she saw, and she says she saw nothing but heard a laugh. He tells her to forget everything, blaming it on Grace Poole.
Of course, Jane does not learn until later that Grace is not really the crazy one, but rather she is charge of crazy Bertha.