Percy Lefroy Mapleton was born on February 23, 1860, in England.

On the afternoon of June 27, 1881, Percy Lefroy Mapleton was involved in the murder of Isaac Frederick Gold on a train. Gold, a 64-year-old retired bakery manager, boarded a first-class smoking compartment. Mapleton, then 21 years old, later joined him in the same compartment. When the train reached Preston Park Station, Mapleton was seen exiting the carriage, appearing distressed and covered in blood. He had lost his hat, collar, and tie, and a gold watch-chain was dangling from his shoe.

Mapleton claimed he had been attacked by two men during the journey. He provided a card that had the name 'Arthur Lefroy.' A ticket collector, Richard Gibson, accompanied him to Brighton, where Mapleton continued to tell his story about being shot during the ride. When questioned about the gold chain, he said he kept it there for safety. He reported the attack to the Brighton police, even offering a reward for the capture of his supposed attackers. A doctor examined him and found only superficial wounds, which raised suspicion.

While investigators reviewed the train compartment, they discovered bullet marks and traces of a struggle, including blood on the footboard and mat. They found coins similar to those on Mapleton, leading to further scrutiny. However, he was not detained immediately and was taken to his cousin's home in Wallington. During this trip, workers found Isaac Gold’s body in a tunnel, where it had been shot and stabbed. His belongings, including a gold watch and a large amount of money, were missing.

After the news of Gold’s murder spread, the hunt for Mapleton began. He was reported missing after he persuaded the officer watching him to wait outside while he changed clothes. This allowed him to escape. The Metropolitan Police took over the case, and media coverage included a description of Mapleton and an artist's impression of him, which led to many false sightings.

On July 8, 1881, Mapleton was finally found in a Stepney lodging house under the name 'Park.' Police officers discovered his bloodstained clothes and evidence of counterfeit coins. When arrested, Mapleton chose not to make a statement but insisted he was not guilty.

Mapleton stood trial at Maidstone Assizes, where he was found guilty in just ten minutes. Witnesses included railway staff who provided evidence against him. The court learned that Mapleton had planned to rob a passenger on the train and had targeted Gold when he could not find a suitable female victim. During the trial, he requested to wear formal clothing, hoping to impress the jury.

Sentenced to death, Mapleton maintained that he had not committed the murder. He was also implicated in another murder but later withdrew the confession. Mapleton was executed by hanging at HM Prison Lewes on November 29, 1881. His body was displayed as a wax model at Madame Tussauds after his execution.