The ​Enemy (Oxford Bookworms)

On a beautiful summer evening in the quiet town of Marlow, a young woman is walking home from church. She passes a man who is looking at the engine of his car. He turns round, smiles at her … and throws acid into her face.
Then her father, the scientist George Ashton, disappears. And her sister, Penny, discovers that her husband-to-be, Malcolm, is a government agent. Why has Ashton disappeared, and why is Malcolm told to hunt for him? Who is George Ashton, anyway?
And who is the enemy?