Every family has secrets. But now someone knows yours.

Abi's daughters couldn't be more different.

She's always felt close to Eva - her confident, older child. It's troubled young Beth that she worries about.

So when foreign exchange student Corinne comes to stay, it's a relief that Beth finally has someone to talk to.

But soon after Corinne's arrival, Abi notices changes creeping in.

Beth starts to misbehave. Eva becomes distant. And everywhere she looks, Abi sees Corinne watching - and listening.

Can Abi trust Corinne? Because if not, she might already know enough to tear this family apart . . .