She was sent to love him. He was recruited to betray her. Neither knows the truth, and both are running out of time.

Claire and Ryan Maddox are celebrating six years of marriage at Niagara Falls. To the outside world, they are the gold standard of devotion: the curated Instagram post on the balcony, champagne at sunset, the effortless banter of a couple who still finds each other's jokes funny. They finish each other's sentences. They bicker over the morning toast. They hold hands with a grip that feels like a promise.

But the woman standing on the balcony is a fabrication.

And the man standing beside her is carrying a weight against his skin—a secret that could cost him the next twenty years of his life.

Over the course of one weekend—seventy-two hours of room service and radio silence, of midnight walks and encrypted glances—a marriage built on the best intentions and the worst deceptions begins to fracture. As the mist from the falls clings to their skin like a second layer of sweat, every conversation becomes a negotiation. Every kiss is a calculation. Every I love you is a confession and a cover story, and the distance between the two is the distance between the railing and the gorge.

As the clock ticks toward a handoff that will change their lives forever, Claire and Ryan circle one another in the most dangerous game two people can play: telling the truth inside a lie, and hoping the lie holds long enough for the truth to matter.

It won't.

LAST NIGHT IN NIAGARA is a breathless psychological thriller about a marriage with two liars, a weekend with no good options, and a waterfall that doesn't care who survives the plunge. It is a story of intimacy disguised as an assignment, and an assignment disguised as intimacy. By the final page, you won't be able to tell the difference.

Because neither can they.