When Lena helps her teenage son gather sounds for his media studies project, she doesn't expect her boom-microphone to pick up a conversation between her neighbours, the Morgans. And she's certain they are planning a crime. Her family and friends tell her that she must have misheard. After all, the Morgans are a well-respected, upstanding couple in their early sixties. They've never been in trouble with the law. Yet Lena can't stop thinking about it. Because what if she hasn't misheard? What if she can prevent something awful happening? After all, stopping it could help ease her conscience about her own dark past.