Don and his team get the drop on a crew robbing high end goods from a FedEx like shipping service, Union Parcel Express (UPE). The crew had struck successfully 23 times, but when the FBI shows up during the robbery two bad guys and one FBI agent end up dead. Confusing the team, the boxes the perps were attempting to steal were empty, leading them to believe that the gang's inside man had double crossed them, angling for a larger cut of the proceeds. They investigate UPE's employees for a lead, and end up meeting Emerson Laidlaw, a mentally handicapped man with savant like abilities. Emerson was responsible for redirecting packages that had shipping labels too damaged to read, and because of his uncanny ability to calculate things in his head, he did the work of six people at once.
Emerson's handicap makes it extremely unlikely that he was actively involved in the scam, but Charlie's math indicates that he was the one feeding information to the gang. They discover that Emerson has an unscrupulous cousin, Carter, with gang affiliations who had been taking advantage of him. It turns out that Carter and his accomplices had set up an elaborate UPE vault heist where they had switched the empty boxes the FBI found for ones full explosive materials. This way, all the equipment they needed to blow in to the vault would already be at the UPE facility during the robbery. The team discovers all of this just in time, and set a sting during the break in that nets them all of the criminals.
