What is the plot and climax and conclusion of The Miracle Worker?
You'll find a detailed discussion of the plot in the Summary section of the enotes study guide to the play. In a nutshell, Anne Sullivan tries to teach the blind and deaf Helen Keller to communicate with the outside world, and succeeds after many challenges.
The climax of the play is when Helen has her great breakthrough, so that she associates words with things (the spelled word "water" with water). The conclusion is that after the breakthrough, Anne and Helen promise to love each other forever, like mother and daughter.