Glace Bay, Nova Scotia, 1904. Willie MacLean is an 12-year-old with a passion for horses and is helping his family get by the best since the death of his older brother in at the local coal mine (the Pit). Willie's older sister, Nellie, is perused by the Scot newcomer Ned Hall, who is always at odds with the mine's owner, Mr. Frawley over the working conditions. Meanwhile, Charley is hiding from the widow MacTavish over her husband's death, while Willie decides to enter his beloved horse, Sable, in a riding competition.
Nellie's Aunt Rose arrives for a visit, and she does not get along with Ned after learning that Nellie lied to her about him being a farmer instead of a miner. But Ned and Nellie's wedding plans hit a snag when Mr. Frawley wants Ned to work on Saturday, (the day of the wedding) and threatens to fire him if Ned takes off. Meanwhile, Willie is angry that Ned is forced to miss their training session for baseball, and Charley has to tutor Willie instead.
Willie and schoolmates, Mollie and Angus, are forced to spend the night in an abandoned house reputed to be haunted on a dare from pit boy Spider. There, Willie thinks he sees his father who advices him that things will get better. Meanwhile, Rose continues to resent Ned, but offers Nellie her mother's prized wedding dress, while Ned is offered to take the day off for his wedding by co-worker Allen, only to have tragedy strike in the mine.
In the aftermath of the recent pit flooding, Ned wants to organize a protest of the working conditions. But Mr. Frawley, and his MORE cynical and nasty boss, Wendell Crowe, only want to keep one section closed and keep the mine operating in fear of loss of profits. As the wedding of Ned and Nellie draws near, Aunt Rose begins to try to talk Nellie out of marrying Ned in fear of being set up for a major heartache. Meanwhile, Willie, Mollie, Angus and other schoolmates prepare to face off against Spider, Strech, Stringy, and the other pit boys in a grudge baseball game.
With Ned unjustly fired as an example by Mr. Frawley, Rose wants to take Maggie, Sarah, and Willie back to Halifax with her. Willie refuses to leave town as does Nellie, until Ned, feeling he's failed her, breaks off their engagement. However, it takes some persuasion by Willie to plead on Mr. Frawley to let Ned have his old job back at the coal mine.
With Ned and Nellie away in nearby Sydney celebrating their honeymoon, the snobbish, city slicker Rose finds herself the center of attention by a traveling violinist, named John Scottie MacNeil, whom she snubs, making Willie and his sisters the center of hostility from the townspeople for treating the legendary musician badly. As Maggie and Sarah prepare to move to Halifax with Rose, Willie seeks the company of Charley where MacNeil persuades Willie to live his difficulties through the magic of music.
After Willie thinks he sees a ghostly pirate ship in the cove, he tries to get Mollie and Angus to help him search for a supposed buried treasure. Only Spider gets to it first, and he ends up being "cursed" by the pirate treasure. Meanwhile, Ned is paired with Mr. Frawley's son, Ben, in the pit where the naive youth from Boston becomes more of a hindrance then a help.
After Willie's horse, Sable, goes missing, Willie suspects that he may have been stolen and he is forced to sneak into the coal mine, disguised at a pit boy miner, to look for his horse, and Ned even tags along to help. Meanwhile, Ben Frawley continues to adjust to life in the mine, while Spider continues searching for the hidden treasure, and Willie continues to resent Nellie and Ned's constant displays of affection in front of him.
Ben vouches for Ned to prove that the pit pony Sable is Willie's horse. Willie becomes determined to find out who stole his horse, and soon discovers that the "treasure" that Spider is still digging on the beach for is in fact stolen loot. Ned thinks there is a connection between the mysterious stolen money and that several pounds of explosive powder is stolen from the mine, and he begins to suspect that Ben is behind the theft to cover for his gambling debts. Meanwhile, Mollie and Angus continue to give Willie the cold shoulder, and Ben Frawley's true colors are ...
More technology comes to Glace Bay starting with a public telephone installed in the lobby of Mrs. MacTavish's train station. After doing a school report on the telephone, Willie writes a letter to the famed Alexander Graham Bell, residing in nearby Baddeck, who invites Willie and his teacher, Anne Harper, to his residence to help share ideas for his new inventions. Meanwhile, Ned is very secretive as he plans to give Nellie a gift for their two-year anniversary when they first met.
Using his new photo camera given to him by Alexander Graham Bell, Willie takes a photo of the old Borso haunted house, and it leads him to try to find out the mystery about the old house which leads him to the late owner's daughter, Helen Borso, who's son happens to be Stringy. When Willie decides to enter a photo contest, a photo he took of Mrs. Borso and Stringy lands in the hands of Miss Harper to submits the photo, without Willie's knowledge. Meanwhile, Nellie continues to try to adjust to using her new washing machine that Ned gave her.
L.B. Collins, a noted newspaper reporter from Halifax, arrives in Glace Bay to interview Willie after his photo of Stringy and his mother make news headlines all over the province as a sign of the horrendous working conditions in the coal mines, which leads to Ms. Collins insisting to Nellie that they explore the mine first-hand to see the working conditions.
When Ned is temporally laid off as the mine puts in new electric wires, Nellie thinks about getting a job. But Ned, due to his pride and ego, strongly opposes her choice to look for work. Meanwhile, Miss Harper sets up a reading class at the mine and tries to persuade Stringy to attend, which puts him at odds with Spider and the other illiterate pit boys who resent education.
Aunt Rose along with Maggie and Sarah arrive back in Glace Bay for Willie's 13th birthday, in which Nellie sees just how impoverished they are as Rose plots to go all out on gifts for Willie which includes a new riding saddle. With Ned incapacitated from the fire at the mine, he resents being taken care of as he recovers, and wants to return to work. Miss Harper also plans to re-set her reading class at the mine, and again tries to persuade Spider to give education a chance. Also, Charley gives Willie a gold plated compass that was left by Mr. MacLean to be given to ...
When Rose offers to buy a large farmhouse for Nellie and Ned, they both find that there are naturally strings attached as Rose wants to model the house the way she wants it to and is not interested in anyone's opinion but her own. Meanwhile, Willie gets a part-time job as an errand boy for Mr. Frawley.
Nellie decides to open her own laundry business, as Willie continues struggling between schoolwork and delivering packages for Mr. Frawley. Meanwhile, Frawley, under orders from the mine owner Wendell Crowe, forces Miss Harper to close down the school at the mine. But Miss Harper, under the advice from Ned, decides to make a stand for her rights.
The evil and greedy Wendell Crowe begins to play hardball with Miss Harper by threatening to having her teaching license revoked unless she stops holding after-shift reading classes for the miners. But it takes some intervention by Ned to play on the little humanity and feelings Mr. Crowe has to let Miss Harper continue teaching. Meanwhile, Nellie's laundry business picks up in full force, while Willie is overwhelmed with helping her, as well as keeping time for his delivery job and schoolwork. It leads to Mollie and Angus playing a mean practical joke on Willie for ...
When Ned is nominated by the miners to run for president of the Provencial Workers Association, his rival, the head wrangler Jack Doyle, plots to use dirty means to win the vote after learning that Mr. Frawley and Mr. Crowe plan to replace some miners with mechanical drillers. Meanwhile, Willie is forced to confront his buried fears about venturing into the mine and he inadvertently and indirectly lets Doyle in on the information Frawley and Crowe have about the new mechanization.
Willie and Charley look after Spider Davis' pit pony, Zack, after he falls ill. Willie asks Helen Borso for some special healing medicine for the horse and asks Mollie and Angus to help him care for Zack. But after Doyle takes the horse back to work in the mine prematurely, Willie must confront his fears of the pit by venturing down into the mine to give Spider's horse the medicine it needs to survive.
Mollie asks Nellie to do a makeover on her in order to shed her tomboy image from hanging around Willie and Angus, and make her into a more of a girl. Meanwhile, Ned begins to resent his co-workers asking him for advice on their own problems with management. Nellie is offered a position as a teaching assistant to Miss Harper, and Spider is unwilling to show his appreciated to Willie in front of his pit boy co-workers in fear of losing his tough reputation with them.
When Nellie's laundry machine goes bust, she tries taking another job as assistant teacher at Miss Harper's school, but learns that there are no funds to pay her. Nellie then takes a job as an assistant telephone operator at the telegraph office at the train station under the supervision of the annoying and obnoxious busybody Mrs. MacTavish, who quickly resents her presence and plots to get rid of her by holding a donation auction at the school to raise the funds needed. When Mr. Frawley donates a brass tobacco spittoon to the auction which was given to him as a gift ...
Maggie MacLean returns unexpectedly from Halifax, and soon finds how everything with Nellie, Willie, and Ned have changed for both the better and worse. Meanwhile, Stringy asks and gets a promotion from Mr. Frawley, but soon learns that the expected increased salary is not what it claimed to be.
Charley finds himself haunted by his past involving the ghost of an old friend who keeps appearing before him involving a 30-year-old tragedy. Meanwhile, Jack Doyle continues alienating the pit boys and the rest of the miners over his callous management issues
Nellie begins to think that she might be pregnant which puts both a glimmer of hope for everyone as Willie and Maggie take over for one evening Nellie's teaching position. Maggie also begins to develop a friendship with pit boy Jimmy. But mystic Helen Borso begins to think otherwise of Nellie's true condition. Meanwhile, Ned is put in charge of a mine face cleaning operation by Mr. Frawley to prevent him from being fired and the end results in a yet another cave-in in which Stringy is badly injured.
With Nellie now bedridden, she fears she may have Scarlet Fever, but is instead diagnosed with consumption. Willie and Maggie are forced to take over Nellie's classes at night, while Mrs. MacTavish phones Aunt Rose and Sarah in Halifax to inform them of Nellie's worsening health. Meanwhile, Ned slowly slides into frustrated and insanity as he and the rest of the pit boys work to clear the mine face on Level 4. With both Stringy as well as Jimmy incapacitated by the recent cave-in and the consumption respectively, Willie decides to make a choice to help Ned.
With Willie back working in the mine as the pit pony driver to cover for Stringy while he's still in the hospital recovering from his injuries, Willie tries to persuade Ned, Spider and the other pit boys to lead a walk-out to protest Mr. Frawley's management. Meanwhile, Rose and Sarah arrives back in town to help Maggie look after the sickly Nellie who begins to doubt her chances of recovery.
In the three months since the victory of the miners strike, Willie's first act as the inaugural president of the Junior Mine Workers Association is to ask Mr. Crowe to send for a doctor trained in treating consumption. However, Spider and the other pit boys want to take advantage of Willie's position to ask to form their own baseball team which they name The Ponies. Meanwhile, Nellie tries to make Rose take Maggie and Sarah away as her health deteriorates. But Maggie refuses to leave and wants to stay in Glace Bay.
The National Coal Company's new doctor arrives in Glace Bay to treat the bedridden Nellie's advanced case of consumption. In a surprising twist of fate, the new physician turns out to be Tony Moressa, Nellie's ex-boyfriend. Tony makes a positive impression on everyone, including Willie, Maggie, and the other pit boys. But not to the gossipy Mrs. MacTavish over some past incidents. Meanwhile, Willie and the rest of the pit boys prepare for their first baseball game as the Ponies.
Willie conducts a dangerous safety investigation in which he has to determine whether one of the seams in the mine contains methane gas. During the safety check, an explosion causes the roof to collapse and Willie is blamed for the damage. Meanwhile, Maggie continues to aid Nellie in her slow recovery and notices Nellie's talent at drawing. Maggie asks Mrs. Borso to borrow a paint box for Nellie.
Wendell Crowe plots to keep Willie working at the Ocean Deeps Mine by having Mr. Frawley give him a raise to take charge of new pit ponies. But Willie's job continues to interfere with his schoolwork and baseball practice. As a result, Willie's combative attitude begins to alienate him from not only his co-workers, but the rest of his friends... including his beloved horse, Sable who takes off. Willie must choose between his job or to find his horse and walk away from it all.
Willie has trouble reconciling his all-too-adult responsibilities with being a kid. Charley takes Willie out fishing to help take his mind off things, including the disappointment that the Ponies are playing a big championship game without him. Maggie and Angus tag along, and things take a turn when Charley injures himself and Willie has to go seek help. Meanwhile, Tony has Mr. Crowe let Stringy work in the mine for a while longer. He has a plan to get Stringy out of the mine for good by having him show off his home run hitting skills at the Ponies upcoming game to a ...
Ned is surprised to find that Spider has been living alone for some time in an abandoned boat. He invites the pit boy home to his house to stay, in which Nellie and Maggie are happy to have company, but Willie isn't. Meanwhile, Nellie continues with her hobby (drawing), and dreams of someday moving into the company house to better her and Ned's lives.
The workers' fight to get adequate medical treatment proves a mixed blessing. The hiring of the company doctor, Tony Moressa, also results in some disadvantages for Ned and the rest of the cash-strapped workers. Tony's exorbitant medical bills are more than the miners can afford. So, Ned is tempted to take another job as the mine's over-man. Meanwhile, Rose and Sarah arrive in town for another visit. Nellie's plans to move into her dream house are quashed when the company buys Nellie's dream house for Tony to live in. Also, Charley is hospitalized with a head injury. ...
Tony helps Ned prepare the Ponies who are about to play in the closing championship game. But the game might have to be forfeited when Ned and Tony get into a heated confrontation over the team's ability to play, and in the aftermath, the Ponies disband. Stringy wonders if he is doomed to be stuck working as a pit boy and seeing his dream as a major league baseball player quashed. But Willie and Maggie scheme to re-form the Ponies with some school mates as replacement players. They ask Stringy to stay on to show off his home-run hitting ability to some scouts from the...
Willie and Maggie conspire to ignite a romance between Charley McGinnis and their school teacher Anne Harper. Their plan revolves around the upcoming school fund raiser. But the annoying, man-hungry Mrs. MacTavish has other ideas. Meanwhile, Ned studies for the over-man's exam with tutoring from Nellie.
Ned feels the weight of his new responsibilities in his new position as the mine's over man. During some dangerous work involving the use of explosives, a "tricked charge" triggers a collapse. Meanwhile, Nellie decides to help Anne Harper form her own school choir when a new piano is installed in the school - and even Spider, Willie and Maggie want in. But Mrs. MacTavish is the only one who sings off-key.
Completely indoctrinated from Aunt Rose's etiquette lessons, Sarah returns from Halifax to stay in Glace Bay, acting pretentious, while Rose travels abroad to Egypt. But Maggie can't stand her sister's fancy and shallow new behavior, and a rift develops between the two sisters. When Sarah loses a family heirloom locket during a theater outing, Angus and Willie decide to play-act as Sherlock Holmes to find where it may be.
When Stringy Borso gets a chance to leave Glace Bay to join a baseball camp down in Massachusetts, Nellie decides that her choir will give its first public performance to send him off in style - in which Angus is made the lead soloist. Unfortunately, Angus discovers he has stage fright. Meanwhile, Ned decides to install new electric lights for the mine despite objections from Cap, Jeremiah, and the other workers over the safety concerns when the pit ponies come down sick with a strange ailment. But eventually, Ned proves how useful the mine's new lights are when they ...
Willie, Maggie, and Spider find themselves lost and stranded on a reef while searching for an endangered eagle's nest. They must figure out a way to get to high ground before a rising tide consumes them, and only Willie's horse, Sable, can raise the alarm. Meanwhile, Ned's new job as over man begins to take its told on the rest of the miners who resent his management tactics and his introduction of the new advances in technology result in more mechanization at the mine.
Theresa Cameron, a gorgeous and talented musician, arrives in Glace Bay right before the annual Fiddler's Fall in which Mr. Frawley, Anne Harper, and Ned will be judges to determine the best fiddler. But the town's assumption that she'll be playing at the event could lead to its cancellation when several fiddlers, including the legendary John Scottie MacNeil, protest the appearance of a woman competitor in the event.
When a wild stallion steals the pit ponies from the mine, Jack Doyle wants to kill the creature and have done with it. Hoping to save the stallion's life, Willie and Charley try to tame the beast. Meanwhile, Ned and Mr. Frawley introduce new technology to the Ocean Deep Mines - new electrical power drills. But fellow minders, Rufus and Scotty, are wary to this change since they don't know how to use them.
Although the modern equipment is supposed to ease the workload in the mine, problems with the machines create new headaches for the miners. When Rufus and Scotty can't handle their coal cutter, they recruit Spider to help. But later, Tony figures out that Spider has been having access to the equipment and the constant roar of the drills have impaired his hearing.
Ned and Nellie unexpectedly receive a bundle of joy at their house when Anne Harper delivers to them an infant whose parents have given up for adoption. Unfortunately, the baby's arrival leads to a confrontation between the couple as they argue about the wisdom of a possible adoption. Meanwhile, Stringy returns from Boston for a visit where he shows Willie a school that may have high hopes for him. Also, Ned begins to feel the pressure when the new technology advancements lay many miners off, leaving them embittered.
In the series final, Willie announces that he has accepted a scholarship to study at the Plymouth School in Boston, majoring in photography. Meanwhile, with layoffs continuing at the mine, Ned ponders a temping offer from Mr. Crowe and Mr. Frawley. But when Ned discusses job securities for the laid off miners, the greedy Mr. Crowe refuses to listen to anyone's opinion but his own, which prompts the miners to stage a massive protest. Also, Nellie is depressed when she learns that her adoption application for the baby has been turned down.