Dr. Jonathan Hemlock, an art professor and mountaineer, is reluctantly drawn back into his former life as an assassin for a shadowy government organization. Hemlock, who has turned to academia to escape his violent past, is blackmailed into accepting a mission to avenge the murder of a friend and fellow operative. The target is one of a group of climbers attempting a treacherous ascent of the Eiger mountain in the Swiss Alps. To identify and eliminate the killer, Hemlock joins an international climbing team under the guise of participating in the expedition.

As Hemlock prepares for the climb, he navigates a web of deception and danger. He interacts with an array of enigmatic characters, including his former lover Jemima Brown and a gregarious old friend, Ben Bowman. The climb up the Eiger becomes a physical and psychological battle as Hemlock faces both nature's formidable challenges and his own moral dilemmas. Tensions mount and trust becomes a precarious commodity as each climber's true intentions gradually surface. As the ascent progresses, Hemlock's determination to complete his mission is tested against the backdrop of the perilous mountain.