John Harper's Grandfather Gerard Harper passes away from typhus.
Unable to pay their rent due to the potato famine, the Harper family is evicted. Shunned by their neighbors, Mary Harper's generosity was forgotten by the very people she helped when they were needy.
John's young sister Ruth dies. John's mother Mary never recovers from the loss.
Mary Harper wastes away from grief.
Unable to feed his family, yet trying to his last breath, John's father Finn passes away, leaving John to fend for himself and his sister Aine.
After converting to Protestantism for a few mouthfuls of soup, John notices the chef has a few broken fingers. He sets and casts them, and in gratitude the man gives John and Aine jobs carrying and stirring soup.
John spills boiling soup on a hand cut from the edge of a cauldron, and notices it heals faster than an identical cut on the other hand.
John attends Queen's college after the Chancellor remembers that Gerard Harper once saved his daughter from a gangrenous wound. John studies medicine and surgery and graduates cum laude in his class.
Unable to find a job and promised a free trip from the chancellor, John sails to America. On the voyage, he meets his future wife Amelia, and when the last bit of water begins to spoil, he saves the crew by straining and boiling the spoiled water after remembering what the boiling soup did to his hand, rendering it drinkable.
John confirms his thoughts that somehow, heated water (or vinegar, as the captain suggests) treats wounds and renders spoiled water drinkable.
John arrives in America.
A passing cobbler hears John remark about his father's work, and offers him an unpaid job with room and board. John accepts.
John saves the life of a pub owner set upon by a bunch of Irish-Hating thugs. John is employed as a waiter, while on the side treating men who have been in bar fights or have been mugged on the streets.
After the pub owner dies, he leaves the pub to John.
After an officer sees what John has done with his patients, he drafts him on the spot, John's worst fear.
John serves as a medic in the Union army, refusing to fire a gun. While on the field he keeps his supplies as well as a means to boil water, and a container of wood ash, a traditional remedy his grandfather used. He notices that (the creosote) wood ash helps with healing as well as boiling water.
John is employed as a professor at the New York Medical College. There, he continues his studies of antiseptic surgery, earning himself a name.
After a long correspondence, John marries Amelia.
John is interviewed by the Medical and Surgical Reporter. John learned a few days earlier from Lister's research that his hypotheses had been correct, and his grandfather's use of wood ash had sterilized the wounds of his patients.
John's love and wife dies of old age.
John Harper dies.
The Year Without Summer allows Finn Harper to get a job as a cobbler and farmer; the landlord who rents his house hires him as another source of food.
The Potato Famine kills almost all of the Harper family, and starts John on his road to the Queen's College and his journey to America. It imparts a lasting fear of being hungry on John.
Queen's College, the source of John's education opens.
Queen Victoria visits Ireland. John is part of the crowd who greets her, and he is crushed by what she does: nothing. He develops a resentment of the aristocracy.
The Civil war, the source of John's field experience. John improves his knowledge of sterile surgery through experience and trial and error.
Pasteur's experiments show that John was correct about boiling water, and it the small organisms that it kills that causes it to be effective in sterilization.
Here John rethinks his opinion of his fellow Irishmen, and continues to help wherever he can. He is seen helping black people, and his pub is looted and burned by the mob of angry people.
John's hypotheses on sterilization are proven.