Since one of his men went down on his watch, Lassiter is determined to find out what happened, and everything points to an unfortunate accident. Shawn, though, seeing the way that Nelson was shot through the heart, knows this had to be murder. He also knows that Lassiter is having similar thoughts but is not letting on.
Back at the office, Shawn recreates the battlefield plan, seeing where everyone was placed and therefore who had a shot at Nelson. The only one who had an angle and was in range was dentist George Cheslow.
Shawn makes Gus an appointment and they go check out George. They find out that George's wife once had an affair with Poe, which gives George motive. But they also find out that he's seriously nearsighted, and Lassiter won't let him wear his glasses on the battlefield because they are not "of the period." There's no way George could have landed a shot that accurate. However, the police find love letters from George's wife at Nelson's house and show up to arrest George anyway.
To prove George's innocence, Shawn and Gus join the regiment to find the real killer. To get outfitted, they go see fellow reenactor Griffin Mahoney, who owns a jewelry store and also supplies uniforms and other memorabilia to the regiments. There, they find Sally Reynolds, who, they learn, is an insurance agent who has written policies for half the regiment, including a multi-million dollar one for Mahoney's store. They also find C4 – to fudge the "cannon blasts" for the audience, Mahoney explains.