Singularity focuses on the relationship of sixteen-year-old brothers, Harry and Barry Kresner, both of whom wish they were not twins. Harry, the novel's narrator, is better at math and science than his brother, but is also more nervous and cautious; he allows himself to be bullied by Barry.

Barry, Harry feels, is sometimes devious and resents having him around.

When the two boys meet anyone new, it is Barry who controls the conversation, while Harry is usually silent. Barry, the handsomer twin, is the one who instantly attracts Lucy Coolidge when they meet her by the river. Nevertheless, it is Harry who figures out what is happening in the playhouse and actually takes advantage of its unusual nature.

Both Harry and Barry are emotionally immature, something that Harry does not realize until late in the novel.

Harry's year-long stay in the playhouse, which takes...