Lydia has been creating her AI, Henry, for years – since before her little brother died in the accident that haunts her nightmares; since before her dad walked out, leaving her and Mum painfully alone; since before her best friend turned into her worst enemy. Now, Henry is strong, clever, loving and scarily capable: Lydia's built herself the perfect boyfriend in a hard-drive filled with lines of code. But what is Henry really – and how far is he willing to go to be everything Lydia desires?