When a young mathematician is killed with a 200-year-old bullet, Castle suspects that time travel is involved. The victim is 25-year-old Daniel Goldstein, an extremely wealthy hedge fund number cruncher, whose clothes were mysteriously removed after he was shot in the chest.
The first suspect is a man named Dandre, whose finger prints were on Daniel’s wallet and who is carrying a gun with him. However, he is quickly struck off the list after an examination of the fatal bullet. Dandre’s gun could not possibly be the Murder weapon because the bullet is extremely odd. It is 200 years old and perfectly round, with accompanying 200-year-old residue.
HG Wells fan Castle immediately thinks time travel, but Beckett brings him down back to planet earth with a list of possible motives for Goldstein’s murder. She establishes that there were plenty of reasons for someone to kill him after his involvement in an investment fund that went wrong for lots of people, especially for gun collector Ivan Podofski.
Podofski insists that he did not kill Goldstein, but reveals that the deceased was also interested in old guns, among many other geeky pursuits. That is confirmed when Castle and Beckett track down Goldstein’s car, a ‘Back to the Future’ style Delorean, and again when they spot a homeless man wearing the victim’s clothes. Bizarrely, the clothes that were stripped from Goldstein's body are part of a turn-of-the-century costume, and the outfit has gun residue on it...
Two bodies rather than one are discovered in a coffin.