With Boyd behind bars, "customers" who purchased his counterfeit plates and currency were faced with a limited supply of counterfeits to pass and no one to make more. One of his "customers" was his brother in law Pete McCartney, a notorious counterfeiter in his own right. Another was James "Big Jim" Kinealy. Kinealy devised a plan to gain Boyd's release. He persuaded Jack Hughes and Terrence Mullen to carry it out. They would go to the Oak Ridge Cemetery in Springfield, Illinois, the site of President Abraham Lincoln's tomb and steal Lincoln's body. Then, they planned to exchange it in trade for Boyd's release from prison along with $200,000. The Secret Service learned of this fantastic plot and decided to discuss the matter with Robert T. Lincoln , the former President only surviving son, since an investigation of this kind was not customarily performed by the Secret Service. It was decided that the Secret Service would need assistance in dealing with these grave robbers. Allan Pinkerton's Detective Agency was contacted. He assigned two men to help. With the aid of local police, Secret Service Operative Tyrrell and former Secret Service Chief Elmer Washborn laid out a plan to catch the robbers in the act. On the night of November 7, 1876, the lawmen, at a distance, surrounded the tomb and waited in the dark. After almost two hours the would-be grave robbers appeared and entered the tomb. With crowbars they managed to move the great stone block that covered the casket. Then, a shot rang out. A detective's percussion cap pistol had fired accidentally. Hearing this, the other police figured the robbers were firing at them, so they returned the fire and for a moment guns blazed at unseen targets. During the confusion, the criminals escaped. Ten days later Mullen and Hughes were caught and ultimately sentenced to a year in prison for grave robbery. Kinealy would eventually also be placed behind bars. At the time, this infamous crime received very little news coverage as it occurred on an election night. The criminals planned it that way. While the townspeople were concentrating on the election, they would commit their deed.
-- United States Secret Service