Singularity, published in 1985 by E. P. Dutton, is a science fiction novel for young adults written by William Sleator.

[1] Sixteen-year-old identical twins Harry and Barry learn that their mysterious great-uncle has died, and his house and possessions now belong to their mother.

Inside the cobweb-filled home, the rival brothers find mysterious animal skeletons and other odd objects.

Outside Uncle Ambrose's residence, Harry and Barry find a small metal-reinforced building, which according to the accompanying keys, is called the "playhouse."

When their quirky and cute neighbor Lucy enters their lives, competition between the twins escalates, and Harry makes a decision that will change the nature of their relationship forever.