Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Depressed Quirkiness
Okay, so we're not totally sure what's going on with the dynamics between the younger couple and the older man, but it definitely strikes us as weird (or quirky) and vaguely depressing. The older man seems unusually friendly toward, and attracted to, the couple (and particularly the young girl), while the young girl—even when calling the older man "desperate"—seems kind of drawn to the older man as well:
The girl closed and then opened her eyes. She pushed her face into the man's shoulder. She pulled the man closer.
"You must be desperate or something," she said. (95-96)
There's definitely some kind of weird attraction going on between these two, but it doesn't seem terribly nice to our eyes. The girl thinks the older man is desperate and tells him so, which isn't the nicest thing to say to your dance partner, and yet she's far from pushing him away. Definitely odd, we think. So with characters that act weirdly and don't seem super happy or healthy in terms of their emotional lives, this story definitely has depressing and quirky cred.