Lucy has found an objective formula for love, but when New York City puts her theory to the test, she discovers new variables she never saw coming.

A college student named Max recounts his childhood memories from the late 1990s, in which he becomes best friends with a boy named Arthur. As Max and Arthur gather both true and fictitious information about Arthur's neighborhood, they begin to dream up fantastical stories and fictional biographies about the eccentric people who live on Arthur's street, a mysterious place called Locust Lane.