Paro and Devdas are childhood friends who are separated when Devdas is sent to school in England. Paro lights a candle that she never lets go out - she says the candle symbolizes Devdas and as long as it remains lit, he will return to her. He returns like 10+ years later when Paro and Devdas are both now adults. The two immediately fall in love and Paro's mother is overjoyed. Devdas's mother, however, is a bitch and extremely jealous of Devdas's relationship with Paro, especially as their family is beneath them economically. Paro's mother approaches Devdas's family and offers them Paro as Devdas's bride, but they reject and mock Paro's mother for even entertaining the thought that they'd let someone of such low birth into their family. Devdas, upon hearing of this, has a huge fight with his parents and angrily leaves the village, leaving Paro with a letter where he says he never loved her.
Devdas begins to spend time in a brothel with his friend and a prostitute named Chandramuki (or something like that) and develops a drinking problem. Chandramuki begins to fall in love with Devdas, but Devdas still loves Paro and, months and months (maybe a year or more??) after he originally left, he returns to his village to apologize to Paro. It turns out Paro is being wed to a wealthy widower who already has grown children of his own. Devdas asks Paro to run away with him, but Paro tells him she would have done so before he selfishly left her. Devdas then sees her being wed and leaves, but not before promising to visit her on her doorstep one last time before he dies.
He returns to the brothel and his drinking problem becomes more severe. Chandramuki, unable to stop him, seeks the help of Paro to get Devdas to stop drinking. She, however, is unable to do much. Paro and Chandramuki become friends and
slay a dance routine, before one of Paro's in-laws, who frequents Chandramuki's brothel, exposes Chandramuki's career and Paro for hanging out with prostitutes. Paro's husband, disgusted and disappointed in Paro, keeps her under house arrest, refusing to let her even take a step outside.
Months later, Devdas has been pretty much been doing nothing but drinking nonstop, and realizing how weak and sick he becomes, he suspects he's nearing the end of his life. He takes a train to Paro's village where, with his final energy, makes it to the front of Paro's house's front gates before he collapses. Paro, who only learns of a sick man laying outside the house days later, calls her stepson into her room to ask him about the man (this happens in the linked video). He tells her it's someone from her home village named Devdas. Stunned, she asks him how he knows and he begins to provide her with the items they found on Devdas (ID, letters from his parents, etc.). Realizing Devdas has come to fulfill his promise to her, the rest of the scene plays out.