When the team from hot tech startup Snoop shows up at the luxury ski resort in the French Alps, the snow is already falling. Not every corporate retreat can take place in such an indulgent location, but when you’re Snoop, and you’re trying to decide between a huge buyout to another tech company or to start another round of funding and keep going at it independently, then you need a place where you can work hard and play hard. And what’s better for that than spending half the day in meetings at the luxury chalet and the other half skiing in the Alps?

Erin and Danny are not impressed by yet another group of young, rich, entitled guests. But Erin’s job to smile and welcome them all, take their bags to their rooms, manage the details of the retreat, and keep everyone happy while Danny cooks the gourmet meals for them. Erin isn’t even all that impressed when Danny explains to her what Snoop is—a music app where you can “listen in on”—or, snoop on—your favorite celebrity’s or influencer’s music in real time. So you can listen to what Jay-Z is listening to right now, or what your best friend is listening to, or some stranger whose musical taste you like. It’s a way to feel close to someone through songs. Erin is skeptical but downloads the app anyway and creates an account.

The group from Snoop seem friendly enough at first. The co-founders Eva and Topher, their assistants, a nerd to do the coding, a social media maven, a lawyer, an accountant, and a free spirited meditation and yoga teacher have clearly all been together for a while. And then there is Liz. Standing apart from the rest of the team, she is not dressed as well, not as confident. She’s one of them, but not one of them, and Erin can definitely tell that there is a story there. But Liz isn’t talking.

For Snoop’s first full day at the resort, they had meetings planned for all morning and then an afternoon of skiing. But Erin points out that the amount of snow that they’d gotten means that they should ski in the morning. More snow was on the way, and there was a good chance that the runs would get shut down later in the day, when it got too dangerous and the risk of avalanche went up. They agree and all hit the slopes, planning to be back for lunch.

Only, Eva never returns.

Erin decides to go to the lift pass office, to check when Eva last used her lift pass, to try to figure out where she is. She doesn’t get very far when the avalanche hits. Most of the chalet is okay, but Danny squeezes out the door to go after Erin. He is able to bring her back to the chalet, but she is injured. And she hadn’t had a chance to talk to anyone, to tell someone that Eva is missing. The only one with cell phone reception is one of the Snoopers, and his is intermittent and sketchy. He finally manages to reach the gendarmes, but he doesn’t know how much information got through.

And then they find Elliot, coder extraordinaire, murdered in his room.

Erin and Danny take the lead in trying to keep people calm and figure out what happened, but the more time they all spend locked together, the more the danger ratchets up. Who will survive until they are rescued?

Ruth Ware’s latest novel, One by One, is a locked-room mystery in the vein of the genius Dame Agatha Christie. Trapped together in the beautiful French Alps, this collection of people have to figure out who the killer is and what their motive is in time to save the rest of the group. This is a masterfully plotted whodunit of the highest order, and it kept me on the edge of my seat until I got to the end.

I absolutely loved this novel, from the power of nature in the setting to the characters to the underlying issues at Snoop. Told in alternating chapters from the perspective of Erin and Liz, two women who are both insiders and outsiders in their own way, One by One offers a glimpse into affluence and opulence, into entitlement and ego, into long-buried secrets and hard-won survival.

If you’re a fan of thrillers, of mysteries, of the iconic Ruth Ware, or just of basic human endurance under extreme conditions, then pick up a copy of One by One. But be careful when you start reading. It’s exceptionally hard to walk away until you get to the end. Be sure to set aside lots of time to get lost in the snow and the desperation of this gripping story.

Egalleys for One by One were provided by Gallery Books through NetGalley, with many thanks.