A young museum assistant is sent by his professor to investigate reports of a large, plesiosaur-like creature seen in a remote Wyoming lake. The account follows his expedition into the Bad Lands, encounters with fossil hunters and guides whose affidavits and newspaper notices mix sober testimony and tall tale, and camp-based efforts to locate remains or secure proof. The narrative combines fieldwork, frontier adventure, and scientific curiosity while exploring the tension between skepticism and the lure of prehistoric mystery.