Aside from Charles Schulz's Peanuts, American comics aren't great at melancholy. I've read plenty of depressing comics, and many upbeat comics, but the gentle downward slope of melancholy seems too subtle for most American cartoonists to capture.

The 20th issue of Chip Zdarsky and Matt Fraction's series Sex Criminals is about a breakup. Neither party seems to want to break up, but they both understand that they have to do it. They have sex, even though they know they shouldn't. They have trouble articulating the things they know they need to say. They are uncomfortable in the moment, and they both know it.

Meanwhile, in another scene, a middle-aged man and woman have sex. She's a retired sex worker. He's an academic. His reaction to her past is getting in the way. She's seen this before. She's tired of it, but she explains it to him anyway.

Sex Criminals has always been a special comic. It's based on a one-note gimmick of a plot — a man and a woman find that they can stop time with their orgasms, so they go on a fuck-fueled bank-robbery spree — but it has somehow expanded to incorporate a rainbow of sexual interests, personalities, and questions about what it means to be human. It's explored adult romantic relationships with a subtlety that most modern literary novels can't touch. The depiction of depression in an early issue felt truer and more honest than most memoir. For those reasons and more, the series continues to be a miracle of the American comics industry.

But issue number 20 is something else again. It has the feel of a deep-autumn Charlie Brown strip (albeit one with explicit illustrations of adult genitalia) and it perfectly captures the responsibility and difficulty of adult life. New readers will be entirely lost — hell, I can't keep track of who all these characters are, and I've been following the book since the beginning — but those who have read the whole thing will find a remarkable maturation in the book's already-mature themes. If Sex Criminals keeps up like this — and if it, uh, climaxes in a, uh, satisfying way — it could be one of the all-time great serialized comics.