Charles Yu will fatally shoot his future self when the latter steps out of a time machine.

Charles Yu lives in a TM-31 Recreational Time Travel Device. He never leaves it, which allows him to live on the edge of time in the Present-Indefinite tense. Charles worries that his Tense Operator is malfunctioning, though he is unsure because he doesn’t feel anything different with his experience of time.

While looking at his exhausted reflection, Charles notices that he is beginning to resemble his father. Charles studied applied science fiction in college to become a structural engineer like his father. When his father suddenly disappeared, however, Charles became a time machine repairman for Time Warner Time, the corporate owner of the universe the novel is set in, Minor Universe 31.

Charles has a dog named Ed. Ed was previously the sidekick of a space western hero, but when the hero became famous, Ed was left to drift toward a black hole, where Charles found him.

The TM-31 has an anthropomorphic computer with two gendered personality interfaces. Charles chose the female interface, TAMMY, because he was attracted to her. The first time Charles ever operated TAMMY, she expressed her inability to lie, then apologized for being incompetent.