During his meditative walks, Marius notices that a man aged somewhere around sixty constantly walks the same route as him, with a 13 or 14 year old girl. Marius finds her fairly ugly and doesn't think about her or the old man much, which is probably good given that he's TWENTY.
And then it all changes. In the second year of seeing the old man and young girl, Marius changes his walking route and goes six months without entering the public gardens. One day, he goes back to his old route and sees and man and girl seated on a garden bench.
But instead of the ugly little girl he used to see, he sees … a beautiful young woman. Guess the awkward phase is over.
Marius pretty much falls in love with the girl right on the spot. After the girl meets his eyes one day, Marius goes home and decides that he needs to put more thought into the way he dresses.
From this point onward, Marius goes to the public gardens with the sole purpose of seeing the beautiful young woman. He sits down at a bench near her and sneaks glances that he hopes the girl's old companion won't notice even though duh, he obviously has, because even people at the oh-so-advanced age of sixty aren't stupid.
Eventually, Marius decides that he needs to know more. He follows the girl home and questions the doorman, but the doorman won't give him any details.
The next time Marius comes to the house, he finds that the old man and beautiful girl have moved away. The pair has stopped coming to the public gardens, too.
Marius gets super depressed, sensing that he's lost the love of his life forever.