Louis Waters is one of Clarissa Vaughan's oldest friends. He's also the former lover and long-term partner of Richard Brown; the two of them were together from their late teens until almost the end of their twenties.
Clarissa remembers nineteen-year-old Louis as having been a "farm-boy fantasy, the living embodiment of lazy-eyed carnality" (1.4)—"a boy Michelangelo would have been pleased to draw" (4.10). When, on the day of her party, she sees Louis again for the first time in years, she thinks:
It has been, what, over five years now, but he's exactly the same. Same electric bristle of white hair, same avid and quirky walk, same careless clothes that somehow look right. His old beauty, his heft and leonine poise, vanished with such surprising suddenness almost two decades ago, and this Louis—white-haired, sinewy, full of furtive, chastened emotions—emerged in much the way a small, unimposing man might jump from the turret of a tank to announce that it was he, not the machine, who flattened your village. Louis, the old object of desire, has always, as it turns out, been this: a drama teacher, a harmless person. (11.7)
Louis may have been a heartthrob back in the day, but time has revealed that there was perhaps not so much mystery about him, after all.
The summer at Wellfleet that Clarissa remembers so vividly was a summer of tangled love affairs between Richard, Louis, and Clarissa herself. Although Clarissa has fond memories of that time, Louis doesn't (11.79). Even Clarissa, when she's being honest with herself, has to admit that it probably wasn't "mere chance" that Louis "cut himself so often that summer, with various tools and kitchen knives," and "required two separate trips to the local doctor for stitches" (8.27).
At nineteen years old, Louis was deeply in love with Richard, and he resented Clarissa's complicated presence in their lives. Now that they are all past fifty, Louis still feels a touch of that old jealousy. After all, Richard chose to spend "the last years of his life" writing a novel about Clarissa (or someone very much like her), and Louis barely gets a cameo in the book (11.23). As the novel's narrator, looking through Louis's eyes, tells us:
All those years with Richard, all that love and effort, and Richard spends the last years of his life writing about a woman with a town house on West Tenth Street. Richard produces a novel that meditates exhaustively on a woman (a fifty-plus-page chapter on shopping for nail polish, which she decides against!) and old Louis W. is relegated to the chorus. Louis W. has one scene, a relatively short one, in which he whines about the paucity of love in the world. (11.23)
Thanks to Richard's book, Louis has the impression that he'll live on in people's memories as "a sad old man complaining about love" (11.23). It's not a particularly flattering portrait, but there are some elements of truth in it: Louis is prone to bouts of sadness, and he does suspect that the world is far less full of love than people like Clarissa choose to believe. So, yeah: Louis is a little blue, but he's not exactly a sad old man. Life's little tragedies just seem to hit him hard, is all.
To find Louis's counterpart in Virginia Woolf's Mrs. Dalloway, look for Peter Walsh: a middle-aged man who once thought that he would marry Clarissa Dalloway, and who still carries a bit of a torch for her, even after more than thirty years.