A homeless man, Richard Starr, sees a terrified woman struggling in rain-swollen Black Creek. As he reaches to pull her ashore she suddenly sinks in the murky water. He dives into the creek but can't find her. Neither can the police. They dismiss his report as a hoax.

Later, Richard learns that his friend, Joe Baker, had been attacked. Joe told a mutual acquaintance he was sleeping under a bridge when the unknown assailant struck. At the time, it was dark, and Joe was drunk and disoriented, so he couldn't tell what was going on, except that he was being dragged into the creek. The...