When several women are found raped and killed, Don asks his genius brother Charlie to help find the killer. Charlie must gain the respect of his brother's team though. They like him, but they are pretty unimpressed when his first 'killer-finding algorithm' pinpoints a local stadium as the perp's home. The murders continue, and Charlie becomes increasingly frustrated at the fact that the math isn't working. Finally, he comes up with a revised equation that sends the agents to the home of one Roland Haldane. While talking to Haldane, Don becomes convinced this is their perp and while looking at the bottom of a knife discovers the marks the rape victims have been branded with. Terry is looking around outside and discovers a fourteenth victim; she is suffocating but still alive when Terry finds her. Roland is shot by Don when he tries to get away. Then Don lets Charlie know that his equation was right, since Roland had moved out of the old neighborhood a few weeks back.