The Lewis and Clark Squad wasn't prepared for what teammate Cody Clark encountered in the River Canyon that day: an injured Chad Levine with his truck and money stolen. Could the unknown visitor who's come to town be to blame? Cody and his friends begin to put some pieces together when they spend the night at Chad's house. Through his telescoped they see suspicious people down by the river. They're even surer something's up when they hear a terrible noise—coming from the river. The kids come up with a plan for identifying the strangers using the telescope, a rusty can of nails, and a goat. If that creative idea doesn't work, they could end up in the middle of something big. And very scary.