The Ringworld Throne (Known Space Series)

In the twenty-ninth century Louis Wu, a 200-year-old scientist became the first human from Known Space to set foot on Ringworld. His exploits there became legendary; in fact it was during his second expedition that Wu saved Ringworld from total destruction. Odd events on Ringworld now once again demand his attention. Incoming spacecraft are being destroyed, the humanoids known as vampires are breeding in alarming numbers and the Ringworld Protectors, who normally st…