Margo Sharpe has a terrible secret. At 16, she played a role in her parents’ violent deaths on Cape Cod. Now a rudderless twenty-something, she’s broke and desperate, reluctantly turning to Craigslist to rent out her second bedroom in Southie. After weeding out the riffraff she decides on Lucy Somers, a shy, deferential schoolteacher. A tentative friendship forms.

Until money goes missing. Relationships are hijacked. Vicious rumors threaten Margo’s job. Then, Lucy disappears. But the threats do not. They get worse. It turns out Lucy snaked her way into Margo’s life for a reason: Lucy knows exactly what Margo did at 16 and is intent on telling the world. That is if Margo can’t get to her first, and silence her.