It's a Wonderful Life

Donna Reed (as Mary Bailey) and James Stewart (playing George Bailey)
In Bedford Falls, New York, on Christmas Eve 1945, George Bailey is suicidal. Prayers for him reach Heaven, where Clarence Odbody, Angel 2nd Class, is assigned to save George in order to earn his angel wings. To prepare Clarence, his superior Joseph shows flashbacks of George's life.
In 1919, 12-year-old George saves his younger brother Harry, who falls through the ice on a frozen pond, from drowning: this heroic act results in George losing his hearing in one ear. One day while working after school at the local drug store, he catches a deadly mistake made by his boss Mr. Gower, who had gotten himself drunk after news of the death of his son in the flu epidemic and accidentally poisoned a prescription.
On Harry's graduation night in 1928, George (James Stewart) discusses his dreams of travel and building things with Mary Hatch (Donna Reed), who has had a crush on him from an early age. After the sudden death of his father, George postpones his plans in order to sort out the affairs of the family business, Bailey Brothers' Building and Loan, a longtime adversary to Henry F. Potter, a greedy banker who is the richest man in town. Potter wishes to dissolve the Building and Loan, which has been preventing him from controlling the entire town. George convinces the board of directors to vote against Potter, which they will do under the condition that George succeed his father, running the business along with his absent-minded uncle William "Billy" (Thomas Mitchell). He gives his college money to Harry, under the agreement that George will attend college after Harry graduates, whereupon Harry will assume the presidency of the Bailey Building &amp; Loan.
When Harry graduates, he brings home a wife, whose father has offered Harry a job. Although Harry vows to decline the offer for the sake of their earlier agreement, George cannot deny him such a great opportunity and keeps running the Building and Loan. George and Mary get married and plan a dream honeymoon, having saved up enough money, but on the way out of town witness a run on the bank and use the money to lend financial support until the bank reopens.
George builds Bailey Park, which offers houses affordable to lower-middle income families who would otherwise have to live in Potter's overpriced apartments. Mary and George welcome the Martinis, a family of Italian immigrants who just bought of one the houses, and have a traditional blessing ceremony. Potter, frustrated at losing control of the housing market, attempts to lure George into becoming his assistant with a huge salary and the prospect of business trips to Europe, appealing to his yearning to travel. George is tempted, but rejects the offer.
During World War II, George is ineligible for service because of his bad ear, and instead leads a recycling campaign to collect metal and rubber for the war effort. Harry, however, becomes a Navy flier and is awarded the Medal of Honor, having intercepted a kamikaze that would have bombed an amphibious transport. On Christmas Eve morning 1945, the town prepares a hero's welcome for Harry. Uncle Billy goes to Potter's bank to deposit $8,000 for the Building and Loan. After bragging to Potter about Harry, Potter angrily grabs the newspaper from Billy along with the $8,000. Realizing the potential scandal would lead to the Building and Loan's downfall, Potter secretly hides the money.
When Uncle Billy cannot find the money, he and George frantically search for it. When the bank examiner arrives to review their records, Uncle Billy panics. George berates his uncle for endangering the Building and Loan, goes home and takes out his frustration on his family. He apologizes to his frightened wife and children, then leaves.




George with his guardian angel Clarence (Henry Travers)
Desperate, George appeals to Potter for a loan. When George claims a life insurance policy as collateral, Potter mockingly says George is worth "more dead than alive". George gets drunk at a local bar, and gets in a fight with the husband of one of his children's teachers (on whom George had unleashed a phone tirade earlier). Mr. Martini, the owner of the bar, ejects George's attacker, but cannot catch up to George, who has driven away and crashes his car into a big tree. He staggers to a nearby bridge to commit suicide. Unbeknownst to him, Clarence has been watching him from the shadows.
Before he can jump, Clarence jumps in the river and pretends to be drowning. George rescues him, but does not believe Clarence's claim to be George's guardian angel. When George wishes he had never been born, Clarence grants his unintentional wish, creating an alternate universe in which George never existed: Bedford Falls is now named Pottersville and is filled with cocktail bars, casinos, and gentlemen's clubs; Mr. Gower has recently been released from prison for manslaughter, having put the poison in the pills because George was not there to catch his mistake; The Building and Loan is defunct, as George never took over after Mr. Bailey's passing. George's friends Ernie, a cab driver, Bert, a policeman, and Nick, a bartender, exist in this reality, but are darker individuals than the good friends he knew, suggesting George was a positive force in their lives.
George runs to see his own mother, who does not recognize him. She reveals that Uncle Billy was institutionalized after the collapse of the Building and Loan. In the cemetery where Bailey Park would have been, George discovers the grave of his brother. Clarence says the soldiers on the transport all died, as Harry was never there to save them, as George had never saved Harry from drowning. Clarence then explains how George single-handedly prevented this dire fate. He, and he alone, kept Potter in check, preventing the town from descending into squalor and vice. Mary never married, and became the local librarian. When George claims he is her husband, she considers him a stalker and screams for the police, causing George to flee and Bert to give chase.
George runs back to the bridge and begs for his life back. His prayer is answered, as Bert catches up to him, but only to say he was glad he found George as everyone was worried about him. George runs through the town joyously, wishing everyone he sees a merry Christmas, and is fine with his forthcoming arrest when he comes home. Mary and Uncle Billy arrive, having rallied the townspeople, who donate more than enough to cover the deficit and for Potter's warrant to be torn up. Harry arrives and toasts George, calling him "the richest man in town." A bell on the Christmas tree rings, and his daughter recalls the story that it means an angel has just earned his wings. George then sees a copy of The Adventures of Tom Sawyer signed by Clarence, who reminds him that "No man is a failure who has friends".

Question: Who never married, and became the local librarian?
Answer: Mary