Henry and Maggie find themselves at a birthday celebration hosted by a local publisher. During the event, the publisher’s son and stepson perform a reenactment of an 18th-century duel. Unbeknownst to them, the antique pistol used in the act has been loaded with an actual musket ball. When the son fires the weapon, he inadvertently kills his stepbrother in front of everyone present. Now, Henry and Maggie must unravel the mystery of who intended for the stepson to die and the motive behind it.