Imagine you meet a young woman with silver hair and a large wad of cash. She tells you she’s older than she looks—a lot older—and she’s just waiting on a phone call before she takes a dive off the Golden Gate Bridge and ends her very long life. Do you believe her? Do you try to stop her?

Such is the central conceit of Tommy Wallach’s new novel, Thanks for the Trouble (Feb. 23).When the mysterious Zelda Toth catches 17-year-old Parker Santé trying to steal from her, she makes him a deal: if he agrees to apply to college, she’ll spend her remaining time and money with him. Parker is skeptical of her claims, but decides to go along with the plan nonetheless—after all, there’s a pretty girl and a bunch of free stuff in it for him. Over the course of Halloween weekend, the pair traverses San Francisco, visiting landmarks, attending a high school party, and trying to suss each other out.

The book went through a number of permutations, including one in which Parker and Zelda travelled the world fleeing a “shadowy cabal of immortals,” but their relationship was always the focus. “I think my book is just a love story,” Wallach says. “It’s complicated and it’s got sci-fi elements and these other elements but at its heart I think it’s just a love story.” Parker is immediately drawn to Zelda and she slowly encourages him to reengage with the world—he has literally stopped speaking since his father died. It’s less immediately obvious what the more vivacious Zelda gets out of the interaction, but it eventually becomes clear that she’s avoiding some very real issues of her own.

In order to keep the story accessible to readers who aren’t as enthused about the supernatural elements (including his mom), Wallach made sure to keep the rest of the novel grounded in reality. His first novel, We All Looked Up, about a group of high schoolers who learn that there’s a 66.6% probability an asteroid will hit Earth and wipe everyone out, employed a similar device—one fantastic element surrounded by an otherwise realistic narrative—so he knew it worked. “Somebody being immortal is slightly more ridiculous than an asteroid,” he says, “but it’s not insanely more ridiculous than an asteroid.”

Before these two novels, Wallach had written six others, none of which sold and all of which he describes as “terrible.” He’s been engaged in one creative endeavor or another since he started playing piano as a kid. In middle and high school, he worked as a member of a professional musical theater troupe. In college, Wallach studied screenwriting and pursued indie rock and fiction writing on his own. He tried his hand professionally at all of these and had little success with any of them. Three months before selling We All Looked Up, Wallach was 30 and about ready to give up. “Everything had just failed, failed, failed and there was no reason to think that anything was getting any better,” he says. “Up until the last second, it just felt like I was banging my head against a wall.” He’s relieved, to say the least, at the success of We All Looked Up and the opportunities it’s brought him.

Wallach is especially excited about the chance to step away from novel writing for bit. “I find writing prose just miserable all the time,” he says. “I tell that to everyone who will listen—even when I go to talk to giant auditoriums full of children.”

Alex Heimbach is a freelance writer in California. Thanks for the Trouble received a starred review in the Nov. 15, 2015, issue.