"They are making ready this very day," said the Eagle, "for the marriage of the daughter of the King of the Blue Mountains. For three years now she has refused to marry anyone whatsoever, until she should give up all hope of the coming of the man who released her from the spell. Now she can wait no longer, for three years is the time that she agreed with her father to remain without marrying."
Your true love promised I Will Wait for You, but you've just heard she's getting married! Is she really that fickle?
No, not really. It's just that she's not allowed not to marry. She may have held out as long as she could and just been forced — or at least coerced — into marriage.
They may have told her "You Have Waited Long Enough" — if, indeed, they were even aware that she had promised to wait.
Good thing that you can show up in time for the wedding, isn't it? This can be the wedding itself, or even the wedding feast, for maximum drama, as long as it is in time to stop the marriage being consummated. Other works may have the true love arrive with as much as several days to spare.
Common in situations where Arranged Marriage is the practice. Though wills with deadlines to marry may also come into play, and family situations where pressure to marry is expected. (If the characters are sympathetic, they may be believe the love to be dead, or be unaware of the relationship.) Royalty may face considerable pressure from courtiers and others who expect an heir to the throne; a prince or princess may face double pressure from their parents.
The heroine may sacrifice herself because her heart is broken, believing the true love to be dead; in that case, the match can be made very quickly after the reported death.
In many Fairy Tales, the hero may be magically induced to forget. The false hero may also force the princess to claim that he rescued her until the true hero shows up to protect her.
Compare The Mourning After. Contrast Absence Makes the Heart Go Yonder, Second Love.
In some versions, the shirt isn't enchanted; the troll bride(s) just literally can't wash things and have them end up cleaner than they started out. The 'dirt' has also been blessed candlewax, which the troll(s) can't remove.
In "Daughter of the Skies", the heroine finishes her quest and arrives during the wedding preparations and bribes the false bride into letting her at her husband; the false bride drugs him twice, but the third time, he is alerted to what she had done the first two, and doesn't drink the drug.
In "The Hoodie-Crow", the heroine finishes her quest, finding the place, and is hired by the cook. She prepares the wedding feast and slips her ring into it; the prince recognizes it and says he must marry her.
In "The White Wolf", the heroine makes it to the castle where the wedding, bribes her way to his room, and pours out her story. The next day, at the wedding feast, the hero marries off his new bride to someone else and keeps the heroine
Then, when all the guests were assembled in the banqueting hall, he spoke to them and said: "Hearken to me, ye kings and princes, for I have something to tell you. I had lost the key of my treasure casket, so I ordered a new one to be made; but I have since found the old one. Now, which of these keys is the better?" Then all the kings and royal guests answered: "Certainly the old key is better than the new one." "Then," said the wolf, "if that is so, my former bride is better than my new one."
Played with in "The Enchanted Snake", where the hero refuses to marry the woman who healed him because he is already pledged to another. Fortunately, they are the same woman.
In The Feather of Finist the Falcon, the heroine arrives to find Finist marrying the Tsar's daughter. She bribes her way to him three times, but the Tsar's daughter has put an enchanted pin in his hair to keep him asleep; the third time, she touched him and knocked the pin out.
Then he summoned all his princes and nobles and his officers of all ranks and told them the story, asking: "Which of these two am I to wed? With which can I spend a long life so happily that it will seem a short one: with her who would deceitfully sell my hours for playthings, or with her who sought me over three times nine lands? Do ye now discuss and decide." And all cried with one voice: "Thou shouldst leave the seller of thy rest and wed her who did follow thee!"
In "The Blue Mountains", the hero arrives on the wedding day of the heroine and bribes a servant to bring her to him. As soon as she recognizes him, they marry instead of her new bridegroom.
In "Maid Maleen", Maleen arrives as the prince is marrying his new bride; her father had locked her in a tower for seven years.
Buttercup in The Princess Bride is forced to marry Humperdinck when she thinks Westley is dead. Fortunately, he shows up to rescue her. Twice.
In Crouching Tiger, Hidden Dragon, Shu Lien had refused to get into a relationship with Mu Bai, because her fiancé (and also Mu Bai's best friend) had died in battle. Mu Bai also refused to get in a relationship with her, to honour his best friend's memory since he felt guilty for not having been able to help him. However, everyone else, including Jen, had invoked this trope to try to get them together. It's a massiveTear Jerker when they finally acknowledge their feelings... when Mu Bai is dying after being poisoned. They can only share a Last Kiss before he goes.
In Cast Away, Chuck makes it through his ordeal by believing that his fiancée is waiting for him back home. Hearbreakingly, she had waited for years after everyone else had given up on him. He's still too late though, as it has still been several years since she gave into the pleas of her family and moved on. Her new life includes a loving husband and daughter.
In "The Adventure of the Noble Bachelor" Sherlock Holmes is called in when a bride disappears within hours after the wedding ceremony. He deduces the existence of the true love, tracks down the couple — who had actually been married before, but she believed him dead — and persuades them to come clean to the rejected bridegroom.
In Edgar Rice Burroughs's A Princess Of Mars, Dejah Thoris agrees to marry another prince, believing John Carter to be dead. He appears and leads on an attack on the city to free her — carefully assuring that someone else kills the prince, since she would be forbidden to marry the man who killed her fiancee.
In the Chivalric RomanceKing Horn, when Horn left his childhood sweetheart, she gave him a magical ring that let him know that he had not lost her. When it changed color, he hurried back and found her being forced to marry.
In "The Sworn Sword" by George R.R. Martin, Lady Rohanne (a.k.a. the Red Widow) will lose her lands if she doesn't remarry by deadline.
In Star Trek: The Original Series, McCoy promised to meet up with Natira, his wife from the generation ship Yonada, when it reached its destination; chronologically, it should've done this shortly after the end of the series. He clearly didn't stay with her from the films, and most Expanded Universe novels say that as High Priestess she was obligated to marry someone else, either before planetfall or because he didn't return.
Inverted in Harry Potter. Harry believes that he will spend the rest of his life fighting Voldemort and Ginny will end up marrying someone else, and he's cool with that. In the end, he defeats Voldemort and he and Ginny wind up married.
Laxdæla Saga and Gunnlaugs Saga Ormstungu both provide examples of this. There may be even more examples. But in both these examples the Hero does NOT get back in time and the love of his life goes to another man; with predictable results, we are talking Vikings after all...
The Odyssey has Penelope being pressured to remarry because her husband is taking too long to come back from his sea voyage. She claims that she'll marry once she finishes weaving a burial shroud for Odysseus' father, meanwhile secretly unraveling the work at night. When her deception is discovered, she says she'll marry the guy who can shoot her husband's bow, that only her husband is strong enough to pull back. Of course, Odysseus arrives in time for the ensuing contest (and righteous slaughter of the pretenders).
In BBC's Robin Hood, Marian has put off getting married for an inordinately long period of time, to the point where the Sheriff can make snarky comments about her being "still a maid" at the grand old age of twenty-one. Robin notes her unmarried status with interest when he returns back from five years fighting in the Holy Land, and even Guy of Gisborne (who coerces a promise of marriage from her) isn't immune to the fact that her singleness is due to the fact that "[she was] once betrothed to Robin Hood".
In Legend of the Seeker, there is an alternate future episode in which Kahlan marries Darken Rahl because Richard is trapped fifty-eight years in the future, with no other way to return.
In the book, she was about to take a man as her mate, because Richard wasn't supposed to return home for about three centuries, and the magic of the Confessors had to live on. Right before she does, she learns Richard is back.
In The Winter's Tale, the king's courtiers attempt to invoke this in the final acts: because he has no heir and is a widower, it is his duty to remarry. Leontes objects, however, that the oracle foretold that he would live without a heir unless his lost child was found, and so remarriage would not succeed. He is heartily supported by Paulina, who knows his wife is still alive.
In one of the endings for Romancing SaGa: Minstrel Song, Farah's mother attempts to convince her to move on with her life rather than keep waiting for her missing Love Interest, and tries to hook her up with another guy. Farah refuses, and the very last scene implies Jamil survived the final battle after all and will come back for her.
In the Gargoyles episode "M.I.A.", Griff travels 50 years into the future. (Destiny, Phoenix Gate, long story) It was strongly hinted that he and Una had something going on in the 40's, but by the 90's, she had taken Leo as her mate. Griff seems to take it all in stride, but it would explain why he wasn't in any hurry to return to London after his adventure with King Arthur.
Some time after J.R.R. Tolkien met his future wife Edith, his guardian forbade them from seeing each other until Tolkien turned 21. After turning 21, he went back to her, only to find out she was engaged. Shortly thereafter, Edith broke her engagement to marry Tolkien.
This happens often in some more conservative cultures in the process of modernizing. For instance, in much of the Middle East, there is great pressure for women to marry before they turn 30 (same principle that informs the Japanese). Many women do find men they would like very much to marry and are personally and socially acceptable to their family...but because, in many of these countries, the economy/job market chronically sucks, he can't find proper work and is thus economically unacceptable (he couldn't support her). So it often happens that women wait for him to get a (better) job...and wait...and wait...and at a certain point the parents (or grandparents) get frustrated and tell her to marry someone else.