It's May, and the river is in flood. Mountain snow melt and torrential rain has plagued the area for a week. Knox Burdette witnesses a murderous attack on a neighbor and Anson Lowell can't let him escape. With no witness, the case falls apart. When one murder has been committed, a second comes at little cost, right? Especially when the witness is a no-account ranch hand. But William Ault lived long enough to press a letter onto Knox and beg him to deliver it to his attorney in Spokane. Knox, being an honest man, undertakes the task.

Knox is trying to escape the gang when a riverbank collapses under his horse. It is Tinker O'Keefe who discovers him clinging to a log. She effects a rescue of both man and horse and takes them in.

The gang, while searching for Knox, shows up at Tinker's house, making threats. The thing is, Tinker's home is a former brothel, and she is painted with the same brush. She hides Knox, and the next day they make their way to Spokane to meet with the attorney.

More surprises are in store, including to whom William Ault has bequeathed his ranch and the discovery of an independent witness to Ault's murder.

Even so, nothing will stop the murderer's urge to kill Knox and Tinker.