Bestselling author Louise Candlish is known for her twists, and if you’ve read Our House (winner of the British Book Awards’ Crime & Thriller Book of the Year and a soon-to-be miniseries), you’re likely already a fan. Her latest, The Other Passenger, is out just in time for summer, and it’s the perfect quick read (a.k.a. a page-turner) to satiate a thriller-loving audience. The novel centres on two couples—one a pair of millennials and the others gen Xers—who develop a friendship via a work commute. Things take a turn when one of the party goes missing and another must recount how this unlikely friendship came to be.

Where did the idea for this story come from?

“I normally have three of four obsessions milling around in my mind, and I’ll sort of wait for an idea to strike to knit them all together. In this case, I really wanted to write a commuter story; I just love the whole idea of those friendships and relationships you strike up when you travel with someone. You have that short period of time on the same mode of transport every day, and you feel like you’re very close and in sync, but actually you don’t know these people at all. And I also wanted to do a kind of modern noir. Another strand was the generational conflict; I chose gen X and millennials because it feels like a raw contrast.”

What research did you do for this novel?

“When I’m writing a story where the criminals are amateurs, which they usually are, and the victims are unwitting or unknowing, I like to keep my own knowledge quite light. I did some research—I probably researched the setting more than anything and knew how many minutes it would take to get from one location to another, so logistically I felt very much in command. But for the other plot points, it was very much from my own mind and instinctive. I try not to wear my research too heavily on the page, but it’s usually there in the background.”

There are some early indications that things are more sinister than they seem…

“When I construct a mystery, I really do think of the reader. I never aim to write a mystery where you couldn’t possibly guess or figure out the outcome for yourself. I like to scatter clues. I’m usually more interested in theme and character than the mechanics of the thriller plot. I always like you to get to the end and think ‘Oh, yes, if I read that again and just highlighted a couple of lines, I could get there myself.’”

Be sure to pick up The Other Passenger, a great summer thriller that will keep you guessing.