Everyone loves inventing a private fantasy place, especially children. It’s a chance to use imagination and create a new world. For twin sisters Cat and El, “Mirrorland” was that place, a secret escape into a dark empty space they made their own, filled with pirates and ships, and strange, wonderful friends. But they invented Mirrorland more out of necessity than fun.

Cat and El grew up in a cavernous house in Edinburgh, Scotland. They don’t remember many good times there, at least outside of Mirrorland. And even inside Mirrorland, they have some scary memories, albeit blurry ones. They remember Mum as tough, although they believed she loved them. But Grandpa --- well, Grandpa was another story entirely. When he drank, he became a monster. When she spoke of those times, Mum called him Blackbeard, and drummed it into them that he was to be feared and they must always stick together.

"What’s to be believed? Oh, it’s a tangled, tangled web with damaged people bent on survival, and a surprising, killer, tingly ending."

Later, El married Ross --- a childhood friend and Cat’s love --- and it broke the twins’ bond. Cat felt angry and spurned; El gloated and acted victorious. Cat moved far away, to California, to escape again, this time not just from Blackbeard, but also from El and Ross. She tried to make a new life there. She knows all about making a new life. But this one is different, and it’s not going as well as she had hoped.

Then things take a turn for the worse. Cat receives word that El has disappeared. She went out on her boat and didn’t come back. Reluctantly, Cat returns to Edinburgh, to the house she never wanted to see again. Once more, El has manipulated Cat. And no one will listen when Cat says that her twin sister is not dead. This is just the kind of thing El does. Not only the disappearing act, but also the emails and notes that Cat keeps finding on the doorstep. Not exactly threatening, but certainly not comforting. When she tells the police, they shrug it off. And Ross disagrees, too, insisting that his wife is dead.

Back when they were kids, El kept a diary. Now she has hidden clues throughout her huge house, pages torn from her diary, with cryptic messages teasing Cat to solve each puzzle. Cat is infuriated by El’s history of controlling her, and now, even as she’s gone missing, she’s still doing it. Ross remains skeptical. The police eventually find the boat scuttled, which to Cat indicates an accident. But where’s El? When a body is recovered, that cinches it for Ross, but Cat still refuses to believe it’s her sister. Only DNA will convince her.

Meanwhile, living in this horrible house from her childhood, she rediscovers Mirrorland. It’s a connection to her sister that she can’t deny. Besides, she has questions. One in particular: What happened that last day, the day before she and El began their new lives? Mirrorland must hold the answers. So she sneaks down into its world of make-believe, where her mind dredges up jumbled memories she lost and perhaps never had. Scenes of role-playing flash through her head. Disturbing scenes of something evil lurking creep in, too, but she has trouble bringing it all into focus and knowing what was real and what wasn’t. Is El somehow playing tricks from the grave? Or is someone else messing with her? Could Ross be behind this? What can be believed?

That’s the question that you, the reader of Carole Johnstone's page-turning debut novel, will be asking yourself: What’s to be believed? Oh, it’s a tangled, tangled web with damaged people bent on survival, and a surprising, killer, tingly ending.