Astrid can't remember the best day of her life: yesterday.

A traumatic car accident erases Astrid's memories of September 9th, the day she spent with an oddly charming stranger named Theo. Ever since, she's been haunted by surreal dreams and an urgent sense that she's forgotten something important.

One night, she gets a mysterious call from Oliver, who knows more about her than he should and claims he can help her remember. She accepts his help, even as she questions his motives and fights a strange attraction to him.

In order to find Theo and piece together that lost day in September, Astrid must navigate a maze of eccentric Boston nightlife, from the seedy corners of Chinatown to a drug-fueled Alice-in-Wonderland-themed party to a club where everyone dresses like the dead. In between headaches and nightmares, she struggles to differentiate between memory, fantasy, and reality, and starts to wonder if Theo really exists.

Eventually, she'll need to choose between continuing her search for him or following her growing feelings for Oliver. Astrid might go to extreme lengths to find what she's lost . . . or might lose even more in her pursuit to remember (like her sanity).