|Referenced|| Chapter 2|
|Relationships||Robert Frobisher, lover|
|Appears||Half-Lives: The First Luisa Rey Mystery|
|Relationships||Megan Sixsmith, niece|
Rufus Sixsmith is the correspondent, friend, lover and accomplice of Robert Frobisher as a young man in the early 1930s. He is featured in Letters from Zedelghem - which consists of chapters 2 and 10, as well as in Half-Lives: The First Luisa Rey Mystery - which consists of chapters 3 and 9.
Sixsmith is first introduced in "Letters from Zedelghem" as the recipient of Frobisher's letters and Frobisher's former lover. He later appears in "Half-Lives: The First Luisa Rey Mystery" as an old man, in the 1970s. He is a prize-winning physicist, who has worked on the "Manhattan Project." His last project is Seaboard's HYDRA Project at Swannekke Island. Realizing the dangers of a nuclear accident inherent in the HYDRA Project, Sixsmith pens an expose and plans to share his findings and shut down the HYDRA. Before he can act, he is murdered in his airport hotel room, where he is waiting for his flight out of the country. The murder is made to appear a suicide. Sixsmith meets Luisa Rey in a chance encounter in an elevator. Learning that she is the daughter of renowned journalist, Lester Rey, on a whim he mails a safety deposit key to her, a key that will lead her to a copy of the HYDRA expose.