After her parents' deaths on Cape Cod, reclusive 20-something Margo Sharpe lives alone in a crap apartment in South Boston. One problem: she can't afford it. So she rents her spare bedroom to Lucy Somers, a shy, allergic-to-everything schoolteacher. At first, they peacefully coexist; Margo manages to keep Lucy at arm's length. But Lucy starts to ask questions about Margo's past. Too many questions. Then, money goes missing. Relationships are hijacked. Dead rats appear all over the house. And it becomes clear, far too late, that Margo chose...poorly.

The Sham is a gripping, head-spinning game of cat and mouse, a nightmare union based on obsession and revenge—a complete sham. Because neither is whom she seems. Who is Lucy Somers, and what exactly does she want?

And who, for that matter, is Margo Sharpe?