As the play opens, the parents of Helen Keller stand looking at her in her crib with a doctor. They discuss the illness that Helen has just recovered from and Kate discovers that because of the illness Helen is unable to see or hear. The second scene, through Aunt Ev and James, Helen's brother, tells us that five and a half years have gone by since the first since, which have resulted in Helen becoming a difficult child to handle because denying her anything causes her to engage in trantrums. Helen and her husband argue about the value of trying any more attempts, with the Captain believing it would be a waste of money, but Helen believes that it is worth trying a governess called Annie Sullivan.
The next scene switches to Boston and to Annie Sullivan as she prepares to leave the Perkins Institute for the Blind, where she herself was a patient and moved from blindness to partial vision. We are presented to her as a character and the way that she is young and has a sense of humour but also haunted by the loss of her young brother, Jimmie, from whom she was separated at an orphanage. Annie is met at the station in Alabama by Kate and James. Kate is worried that Annie is too young, but Annie assures her she has lots of energy and also she has the experience of being blind. Kate and Annie begin to like each other.
As Annie meets Helen, she teaches her how to hand-spell "doll" and "cake" and then is hit by Helen and locked in. Annie has to be let out by a ladder brought to her window. Annie finds Helen next to the well, her favourite place, and watches as Helen, unaware of Annie's presence, removes the key to the room that she locked from her mouth and throws it down the well. Annie smiles, and the stage directions tell us that she does this with "great respect, humour, and acceptance of challenge," and goes back into the house, leaving Helen by herself as Act I ends.