Timothy Warner, a PhD student who goes by the nickname Moth, wakes up on his ninety-ninth day of sobriety with an intense craving for drink. He immediately calls his uncle Ed, a former alcoholic and now successful psychiatrist who has become Moth's mentor and father figure. Ed promises to meet him at an AA meeting later that day but never shows up. Moth bikes to his office only to discover a grisly scene—his uncle lying in a pool of blood, shot through the temple. Deeply shaken, Moth dials 911 and waits for the police, who pronounce the death a suicide. Two words are scrawled across Ed's prescription pad: My fault. But Moth refuses to believe that his uncle would take his own life. Devastated and confused, he calls on the only person he thinks he can trust: Andrea Martine, an ex-girlfriend he has not spoken to in four years, a young woman who is struggling through her own trauma.

Each battling their inner demons, Moth and Andy travel into dark, unfamiliar territory, intent on finding out the truth about Ed's death and circling ever closer to a devious mind that will flinch at nothing to achieve his own goal of revenge.