Trip Fontaine's the best developed of the male characters in the novel. The narrators know Trip from boyhood as a pudgy, weird-looking kid, but in the year before the suicides, he "had emerged from baby fat to the delight of girls and women alike" (3.32). Trip gets a lot of ink in the novel, because the boys are amazed at how girls throw themselves at him, but more important, because he turns out to be their intro to the Lisbon sisters.
Trip has an exotic history. He becomes the school heartthrob after a trip to Acapulco with his father and his father's boyfriend Donald, where he manages to seduce a 37-year-old woman at a hotel bar. Or rather, she seduces him. He comes back to school as a tall, deep-voiced golden boy who drives the girls crazy:
Before long he lived like a pasha, accepting tribute at the court of his synthetic coverlet: small bills filched from mothers' purses, bags of dope, graduation rings, Rice Krispie treats wrapped in wax paper, vials of amyl nitrate […] (3.35)
Trip starts a thriving drug-dealing business and leaves school three times a day to smoke weed in his car. The boys are fascinated by him. Trip's father ignores the parade of girls to Trip's bedroom. The boys think it's probably because the "iffiness of his own conduct" (3.35), i.e. being gay in the 1970s in a conservative suburb, made him pretty non-judgmental. Trip and his father are more like roommates, floating on air mattresses in the pool, wearing matching peacock robes and towel turbans, getting tanned within an inch of their lives.
The boys admire Trip for never, ever talking about the girls he bedded, unlike most boys who broadcast that stuff to everyone. They figure it's because living with a gay father made him learn to be private about his sex life.
Just saying that they knew Trip Fontaine was enough to make girls grab at the narrators. He was hot:
No boy was ever so cool or aloof. Fontaine gave off the sense of having graduated to the next stage of life, of having his hands thrust into the heart of the real world, whereas the rest of us were still memorizing quotations and grade-grubbing. (3.39)
Trip's cool is blown when he meets Lux. He can't explain it, but he's totally undone the first time he sees her. He's at a loss about what to do—girls always ran after him, so he's not used to having to pursue anyone, especially someone like Lux.
Even the wimpiest boys were more adept than Trip at asking girls out. […] Trip had never even had to dial a girl's phone number. […] He had never felt the pain of lackluster responses, the dread of "Oh… hi," or the quick annihilation of "Who?" His beauty had left him without cunning […]. (3.50)
Trip can't understand why Lux affects him like that. He describes it to the boys in terms of auras and atoms breaking apart; the boys attribute that to his always being high. Anyway, he finally tells Lux he's going to ask her father to take her out. He spends a quiet evening at the Lisbon house not even sitting next to Lux, but after he leaves she follows him to the car and jumps on him:
Even though that lightning attack lasted only three minutes, it left its mark on him. He spoke of it as one might speak of a religious experience, a visitation or vision, any rupture into this life fro beyond that cannot be described in words. "Sometimes I think I dreamed it," he told us […] (3.58)
Lux is grounded after that night, and Trip has to wait until next fall, when he persuades Mr. Lisbon to let the girls go to the Homecoming dance on a group date so he can be with Lux. This is a big breakthrough for the lucky boys who Trip picks to take the other three sisters. Of course, Trip and Lux get named King and Queen of the prom. He and Lux sneak off after the dance and have sex on the football field, but after she starts to cry in the middle of it, he suddenly gets turned off and leaves her there. It's inexplicable.
"I walked home that night. I didn't care how she got home. I just took off." Then, "It's weird. I mean, I liked her. I really liked her. I just got sick of her just then." (3.222)
The boys don't learn about this until years later. They know that Lux missed curfew that night and brought on the imprisonment in their house that doomed the sisters, but they didn't know why she didn't make it home. By the time they get around to interviewing Trip about his relationship with Lux, he's spent years in rehab and looks way the worse for wear. He's got the shakes and his skin is yellow. Listen and learn, Shmoopers: drugs are bad, m'kay?