In classroom science laboratories, unlike a real science laboratory, the teacher can guide students away from potential dead ends and toward data that are most likely to result in accurate conclusions. Sometimes, though, allowing students to pursue dead ends and to collect "bad" data can provide especially rich learning opportunities. This article describes an inquiry-based physics laboratory activity that intentionally allowed students to go down an erroneous path. The author used this laboratory in a high school physics class over four days to examine Newton's second law: the acceleration of an object is equal to the net force acting on the object divided by its mass. Prior to this activity, students had an understanding of constant-velocity motion and constant-acceleration motion. They had also learned Newton's first law and the idea of a net force but had not yet addressed Newton's second law or how to address unbalanced force situations. Based on their knowledge of Newton's first law, students could surmise that unbalanced forces would lead to acceleration, but what would the size of the acceleration be? This question motivated the laboratory investigation described, and the goal was for students to empirically develop a mathematical formulation of Newton's second law, not simply confirm it.