The stories about Beowulf Shaeffer are part of Niven's Tales of Known Space, a vast series of stories and novels that tell of humanity's expansion into the galaxy. The stories of Beowulf Shaeffer take place during the early period of contact with the mysterious, and very cowardly, Puppeteers. One of Niven's most popular stories, "Neutron Star," involves the Puppeteers blackmailing Shaeffer into uncovering what is killing crews near a neutron star. Each of Shaeffer's adventures is humorous, each usually has a scientific concept at its center, and each involves reluctant derring-do by Shaeffer. As "The Borderland of Sol" indicates, in the time of Beowulf Shaeffer, humanity has colonized only a small number of worlds but has already defeated the Kzin in war.