The play opens with Doctor Colenso Ridgeon having been recently knighted. He has seemingly developed a cure for tuberculosis. After meeting with Sir Patrick Cullen a retired physician, Ridgeon allows Jennifer Dubedat to see him, though he is reluctant and only sees her at the insistence of Emmy, his serving-woman. Upon meeting Jennifer she asks the newly knighted doctor to save her husband, Louis Dubedat of tuberculosis. He is a man, she says of great artistic genius and she believes Dr. Ridgeon is the only man that can save him. Once Ridgeon sees his drawings, and in particular one of Mrs. Dubedat. He agrees to have the young married couple come to a private dinner he's arranged with his fellow physicians to celebrate his knighthood. There, he and his colleagues will determine if Louis is a man worth saving as Ridgeon only has 10 spaces available for his cure and he cannot spare any more.
At the dinner Louis and Jennifer charm each and every one of the doctors before being sent home in order that his tuberculosis does not get worse. Once Louis and Jennifer have left, Dr. Blekinsop attempts to catch them. He returns to the other, wealthier doctors having been discussing how Louis has borrowed money from them all in the same evening and they gladly gave it to him as they were quite charmed by him. Blekinsop reveals that he lent the young artist all the money he had been scraping up in order to take the train home and the young man was meant to repay him but never did.
We then are introduced to Minnie Tinwell who says that Louis Dubedat is her legal husband and she has the marriage certificate to prove it. These sequential findings continue to stack up and the doctors are left with a dilemma once they discover that Dr. Blekinsop himself has tuberculosis. The dilemma for Ridgeon has become whether to save Dubedat a budding genius of an artist who appears to have little honor or Blekinsop an honorable man who is an average doctor. And, Ridgeon's judgement is clouded by the fact that he desires to marry Jennifer.
Thus, the group of doctor's set out for the Dubedat residence in order to get to the bottom of their findings. Dubedat continues to charm them and admits that he was married to Minnie, but that they had agreed to end their relationship. During the questioning of his character by the doctors, Louis draws a portrait of Sir Patrick which he sells to Bonington. Ridgeon, upon Jennifer's return says that Bonington will take care of her husband's tuberculosis. She wants Ridgeon to do it as she believes he is the only one who can actually cure him, but she trusts his judgement and agrees to Bonington's care not knowing that Ridgeon's treatments must be done in a sequential manner to bring about a cure. This sequence is one not known to Bonington.
Soon, Louis succumbs to the disease and is on his deathbed with mere moments remaining in his life. He tells his wife to marry again if she found marriage to be pleasant with him and not to speak of him to her new husband for he will be jealous. He also asks her not to wear mourning clothes, but to always dress beautifully so that others would say that she was married to Louis Dubedat. Louis dies resting his head in her bosom. Jennifer then goes to change in order to immediately be as her late husband asked her to be and she bids farewell to her friends, but does not consider Ridgeon to be a friend as she knows of his deceit.
The following season, Louis' work is being displayed in a one man show put on by Jennifer. Ridgeon arrives early to purchase his work and makes a belittling comment to the curator about Louis that Jennifer overhears. When Ridgeon and Jennifer are alone he admits that he killed Louis by not treating him himself, that he knew Bonington would fudge the treatment and thus Louis would die. And that he did it because he was in love with her. She finds that appalling as he is an older man and she so young. He tells her he has marked the works he will purchase, but she won't allow Louis' works to be sold to him. She then reveals that she has remarried as Louis wished. Ridgeon begins to speak, needing to say something to her, but decides against it and leaves.
