Samuel Langhorne Clemens (30 November 1835 – 21 April 1910), better known by his pen name Mark Twain, was an American author and humorist.
Sometime prior to 1863, Twain became acquainted with Horace Greeley, having worked with him in the New-York Tribune, which was founded by Greeley. During the New York City draft riots, he lived upstate with his wife Olivia.
In 1872, Twain encountered the Pinkerton agent Tommy Greyling during a boat trip from New York City to London. The two discussed Greeley, who was a mutual friend, and his murder. Greyling had been sent from the United Kingdom to investigate the crime and Twain offered to help him after hearing about the Pieces of Eden, which Twain heard about during his travels in the Mediterranean and the Holy Land.
A few days later, Greyling and Twain partnered with Detective Frederick Abberline and the Assassins Evie Frye and Henry Green, chasing the Templar agent who tried to murder Greeley across the city. The group tried to prevent Alice from stealing pages of the Voynich manuscript hidden in the British Museum. While they ultimately failed, Greyling later cornered Alice on the boat bringing her back to America.