Art Woo, thirty-eight years old, Asian-American, and a salesman in a dying industry, finds himself housed in a welfare hotel during a sales convention--the unexpected result of trying to limit travel expenses for his company. His modus operandi is to "maintain a certain perspective," so he attempts to make the best of the situation.

We learn that his wife, Lisa, has divorced him--the outcome of Art's inability to grieve along with her when, after many months of fertility treatments and two miscarriages, Lisa's successful pregnancy was medically terminated at four and a half months because the fetus was afflicted with a severe genetic abnormality. Whereas Art reacted with hope for having another child, Lisa had seen only loss. Likewise, when his boss had insulted Art with a racial slur, Art had maintained "perspective," while Lisa thought he should have quit his job.

The "birthmate" of the title is Billy Shore, four years younger, American, and a business rival. Billy is obnoxious, but has advanced to a new job. Art thinks that if Billy can get ahead, so can he. But Art's equilibrium is ultimately destroyed by an experience in the welfare hotel. He realizes that he has lost not just a job opportunity and his wife, but also his child.