SCENE 1 - Outside a rural Massachusetts church in 1900, Henrietta, a woman in her 30s, is marveling at the sky. Her sister, Margaret, sneaks up on her and asks why she isn't inside the church. Henrietta reveals that she has been sent a letter from Harvard offering her a job at the Harvard Observatory, she is good at math. Margaret is skeptical and tries to talk her out of it. Henrietta asks her if she wants to go with her, Margaret says no. Henrietta then asks if she will help convince father to give her her dowry money in order to go. Margaret reluctantly says she will help.
SCENE 2 - Henrietta arrives at the Observatory and meets Peter, who works under the main astronomer, Mr. Pickering. After he tells her that she will not be using the telescope and will be studying glass photographic plates from the telescope in this room with other women, calling them a harem, Peter and Henrietta realize they have gotten off on the wrong foot. But she does share her passion for the sky and physics and Peter, taken aback by her directness, blurts out that he always wanted to do Gilbert and Sullivan. The other ladies arrive. She meets Annie and Williamina who co run this department and were some of the first to make a categorizing system for the stars. Henrietta has learned about their classification system and is honored to meet them. They start working. This leads us to a passage of time, with overlapping dialogue. The women keep discovering stars, Peter keeps making his rounds, he is obviously always interested in talking to Henrietta, and Henrietta receives letters from Margaret who begs her to come visit and finally announces that she has had a baby.
Scene 3: Peter and Annie discover Henrietta asleep at her desk. She has been working long hours mapping the brightness of stars. Everyone is impressed with her work. After she leaves to go take a nap. Peter reenters, excited. Einstein’s “Theory of relativity” has just come out and Peter is inspired by the possibilities of what could be out there.
SCENE 4: Henrietta is at work late. She is crying. Annie comes in to grab something she left. She asks why she is crying. She explains that she has spent years recording the brightness of these stars, trying to find a pattern but can not find it. It feels hopeless. Annie encourages her to keep going. After she leaves Peter comes in. They talk but you can tell that Peter wants to tell her how much he loves her, he finally does, then he blurts out that he wants her to join him on a ocean liner to Europe and meet astronomers from around the world. Henrietta says she must stay and keep working. Just as she is about to give in and go, she receives news from home that her father has had a stroke and she must go home.
SCENE - 5 Henrietta arrives back home. Margaret has said it has been hard managing alone but is relieved that she is home to help. More time passes as Henrietta works from their home. Harvard sends her more of the glass plates to continue her work. She also writes to Peter and sometimes hears back. SCENE 6 - It isn't until one night that Maraget shares what she has been working on to Henrietta. She has composed a symphony. As she plays it for Henrietta it all clicks. She realizes that all of these “winking stars'' that seem to have no patterns are like notes. She realizes that the length between the wink may correspond to how bright a star is and by comparing them they may be able to tell how far away a star is. The first act ends with this discovery and the reactions of her fellow colleagues, Annie and Williamia and Peter.
ACT II SCENE 1 - The scene starts on an ocean liner in 1910 Peter enjoys Henrietta on deck under the stars. Everything is well and romantic until the ocean liner fades away and she is back in the observatory. Peter enters and he is now cold and formal. Henrietta has been away for years now. Peter is hurt but it is still clear that he loves her. Williamina comes in excited by Henrietta's most recent published article about her discovery. Peter continues saying harsh and demeaning things. As he is leaving he says he must go home to his wife. Henrietta drops one of the glass plates upon hearing this. Annie enters wearing a “Vote for women” sash.The observatory drops away as we see Peter start to give a lecture on the vastness of the universe. At first Henrietta talks to him as if they were in conversation, his lines from his lecture becomes his dialogue. Soon Henrietta sits, now watching his speech. He finishes his speech adamant that the universe can not be bigger than the milky way. Henrietta approaches him after his speech to ask how he could be so narrow minded to think that. Peter disarms her by saying he is sorry that he married, it was not an easy choice. He also apologies that he was rude upon her return. Henrietta announces that she has just decided to take an ocean liner to Europe. Peter says what she is doing is very important and that he is proud of her.
SCENE 2- Henrietta arrives back in Boston from her cruise. Now with Annie and Williamina. She is met by Margaret. Henrietta has a few waves of pain, which she explains to Margaret, comes and goes. In a short moment we see that she is also still in contact with Peter through letters.