Seeking a fresh start for their marriage, Briton Anna and her Australian husband Jake move to Melbourne with their two small children. With Anna resuming her career, they hire a young live-in nanny to help - but local girl Becky is anything but the innocent stranger she pretends to be.

Lulled into a false sense of security, Anna recommits to Jake. She continues to confide in Becky, unaware that Becky is under Jake's spell and plotting together with him against her. Later, a shocking turn of events leads Anna to discover the truth of what is going on, and she decides she is not going to be a victim any more.

Becky is conflicted when Anna tells her that Jake is physically abusive, showing her a bruise on her shoulder and claiming that Jake hit her. When Jake lures Becky back, Anna realises she has to take drastic measures to protect her children and comes up with a deadly plan.

Becky helps Anna set up an apartment where she is safe from Jake, and on the day Anna is due to move out and take the kids, she asks Becky to stay at home with Jake.