Rivers, oceans, streams, lakes--it doesn't matter what shape it takes, Em Hansen is terrified of the water. She hasn't shared her phobia with her new husband, Fritz, and when his best friend, Tiny, organizes a month-long, private, white-water rafting trip through the Grand Canyon as a wedding gift, she can't tell him how awful the trip sounds. Fritz and Tiny cobble together a party of fourteen people for the trip, but at the last minute, Tiny finds himself in the hospital and has to miss the trip. He fills his spot with George "Wink" Oberley, ostensibly a geology Ph.D. candidate at Princeton and expert river rafter, but Em immediately suspects there's more to his story. Then the rafting trip Em had been trying so hard to enjoy veers further off course than she had ever expected: Someone disappears from their party, and a dead body washes up downstream. Now it's up to Em to figure out what happened--and whether she and her husband and stepson are sharing rafts, food supplies, and tents with a murderer.