- "Somehow, through the darkness and the stars, Marty saw a pair of dust-covered boots. / 'Maggie!' a man's voice called overhead. 'Fetch some water! We've a hurt man here!' / Somehow, Marty managed to turn his head enough to look at the man kneeling over him. The fellow was wearing overalls and a workshirt, and a round hat — sort of a derby, except it was made out of straw. He was probably only a few years older than Marty, although it was hard to tell with the fellow's full, red beard. But there was something more, something oddly familiar about this farmer. If only Marty could think, he'd put his finger on it right away."
- —From Back to the Future Part III by Craig Shaw Gardner (quote, page 47)
Seamus McFly was the husband to Maggie McFly. He was Irish by birth and together with his brother Martin moved to the United States from Ireland in the 1880s. Seamus appeared to be in his mid-twenties to early-thirties in 1885, and his religion was the Roman Catholic faith.
Seamus was an optimist, who usually looked on the bright side of life — he did, however, walk away from a fight rather than being goaded into one. This was not because he was a coward, but because he knew it did not matter what other people thought of him. Also, he remembered how his brother Martin McFly (who always loved getting into fights) had been killed in Virginia City, Nevada after getting into a fight.
Seamus's name would be given to Marty as a middle name, presumably by George.
Seamus, Maggie and Seamus's brother Martin left Ballybowhill, Ireland in the early 1880s with hopes of a better life. They gradually headed west, eventually ending up in Hill Valley, California, although it is unknown exactly when they arrived there.
They either lived in, or passed through, Virginia City, Nevada before arriving in Hill Valley. It was there that Martin McFly lost his life — whilst trying to prove that he wasn't a chicken, he was stabbed in a saloon with a bowie knife. This had an effect on Seamus as well, who remembered his brother and tried not to make the same mistake. Seamus encouraged others to learn from Martin's mistake, and to not let what other people think of them take over their lives.
After settling into Hill Valley, they lived and worked in a farmhouse 14 miles outside of town, together with their son, William, who was born in April 1885, "the first McFly to be born in America". Since William was a few months old by September 1885, and the townspeople knew the McFlys quite well, they may have been living in Hill Valley for a couple of years by 1885. The couple worked hard on their farm, often going into town - where local outlaw Buford "Mad Dog" Tannen aside, they were liked by all the townspeople.
Tannen took a dislike to Seamus for some unknown reason, and told Seamus not to step into the Palace Saloon. Seamus, however, did not appear to take much notice of Buford, and the two men never actually encountered each other.
Seamus and Maggie first met Marty McFly on September 2, 1885, who had time travelled back from 1955 (and originally from 1985), when he crashed into their fence whilst running from a bear. Seamus found Marty unconscious, and he and Maggie took him in, putting him in their bedroom were he recovered while Seamus went hunting for their "supper".
After Marty woke up, he discovered who his great-great grandparents were. As he couldn't tell them his real name, he called himself "Clint Eastwood". Seamus in particular had a feeling about Marty, that they should look after him — especially after seeing Marty hold William, who normally hated strangers. Seamus and Maggie let "Clint" stay in their barn overnight, after telling him about his friend Doc Brown being the local blacksmith in town. The next morning, Seamus gave "Clint" a lift to the railroad tracks into Hill Valley.
Seamus and Maggie went into town themselves two days later for the Hill Valley Festival, which was celebrating the arrival of the new Courthouse clock. There, they met "Clint" again (who had found Doc by this stage). Buford Tannen showed up and after trying to shoot Doc, challenged Marty to a duel by calling him yellow. Seamus and Maggie overheard this, and afterwards told Marty the story of his namesake Martin in Virginia City, suggesting to Marty that he start thinking about his future.
Seamus met Marty for the final time on Monday, September 7, as he arrived into town to watch the duel between Marty and Buford. His "funny feeling" had returned, making him feel he had to be there — "as if my future had something to do with it". Whilst the other bar patrons were trying to get Marty to go out and fight Tannen, because otherwise he would be regarded a coward, Seamus encouraged Marty to make his own decision. Marty realized that it did not matter what people thought of him, and decided not to fight Tannen.
Marty ended up in a duel with Tannen anyway, this time to save Doc rather than prove he was not a coward, and he defeated Tannen by using his mind instead. Afterwards, Marty gave Seamus his unused gun — "worth $12, never been used" — and Seamus decided to trade it for a new hat. Marty's final word to Seamus was to take good care of their baby.
In 1931, his son William referred to him in the past tense, implying that he had died by then.
Wanting to get Marty a gift for his high school graduation of 1986, Doc did research for a book that he was putting together titled The McFlys of Hill Valley. As such, Seamus and his family were the first McFlys to be documented in the book.
Behind the scenes
- By 1989, when Part III was filmed, actor Michael J. Fox was 28 years old. As Seamus, he was able to portray a character closer to Fox's age, who gave advice to the less mature, 17-year-old Marty McFly, also played by Fox.
- Crispin Glover was the original actor cast as Seamus, to make both Marty's parents and great-grandparents played by the same actors. As salary issues caused Glover to drop out, this led to Michael J. Fox playing his fourth McFly (as in Part II he played Marty's children Marty Jr. and Marlene). He reprised this role years later for the video game LEGO Dimensions.
- It is never established in the Back to the Future Part III screenplay, nor in the novelization, how old Seamus and Maggie might be, nor when they came to the United States or to Hill Valley.
- The novelization states that Seamus and Maggie were from Ballybowhill, Ireland. The location is more often spelled as "Ballyboghill", but pronounced the same.
- Seamus is seen as one of the bravest of the McFly family as he had virtually no fear of his Tannen tormentor, and cared little of what others thought of him. William seemed to take after him in that regard (although, he didn't seem to have a member of the Tannen family antagonizing him).
- Back to the Future Part III
- Back to the Future: The Game
- Back to the Future: The Game - Episode 5: OUTATIME (Mentioned only)
- LEGO Dimensions (Non-canonical appearance)
- Harold McFly (medieval ancestor)
- Jennivere McFly (medieval ancestor)
- Martin McFly (brother)
- Pee Wee McFly (nephew)
- Maggie McFly (wife)
- William McFly (son)
- Arthur McFly (grandson)
- Sylvia McFly (granddaughter-in-law)
- George McFly (great-grandson)
- Lorraine Baines McFly (great-granddaughter-in-law)
- Dave McFly (great-great-grandson)
- Linda McFly (great-great-granddaughter)
- Marty McFly (great-great-grandson)
- Jennifer Parker (great-great-granddaughter-in-law)
- Marlene McFly (great-great-great-granddaughter)
- Marty McFly Jr. (great-great-great-grandson)
- Marta McFly (great-great-great-great-great-granddaughter)
Notes and references
- ↑ In Back to the Future: The Game - Episode 3: Citizen Brown, Marty is referred to by Edna as Martin Seamus McFly
- ↑ 
- ↑ Back to the Future: The Game - Episode 5: OUTATIME
| The McFly Family|
Marty McFly | George McFly | Lorraine Baines McFly | Jennifer Parker | Seamus McFly | Maggie McFly
Dave McFly | Linda McFly | Martin McFly, Jr. | Marlene McFly | Arthur McFly
| The Brown Family|
Dr. Emmett "Doc" Brown | Clara Clayton Brown | Jules Brown | Verne Brown | Einstein
| The Tannen Family|
Biff Tannen | Buford Tannen | Griff Tannen | Irving "Kid" Tannen
| The Strickland Family|
James Strickland | Roger Strickland | Irene Strickland | Edna Strickland | Gerald Strickland
Match, Skinhead & 3-D | Goldie Wilson | Douglas J. Needles