She thought she knew him—until he locked the door. Sophie Hale is weeks away from her dream wedding to the perfect man, Ethan Cole. Their life in a beautiful city apartment is a carefully curated picture of happiness, a sanctuary from the ghosts of her past. He knows how she likes her coffee, the color that brings out her eyes, the fears she keeps locked away. But when cracks begin to appear in their perfect facade—a misplaced ring, silent phone calls in the dead of night, an email she doesn’t remember writing—Sophie's world starts to feel less like a sanctuary and more like a perfectly constructed cage. Her fiancé’s attentiveness feels like surveillance, his love like a form of control. The true terror begins with a whispered phone call from a stranger claiming to be the real Ethan, warning her that the man she shares her bed with is a dangerous impostor. Trapped in her own home with a man who seems to know her every secret and weakness, Sophie is plunged into a terrifying psychological game where every memory is a weapon. Is she losing her mind, as he so lovingly suggests? Or is she the victim of a deception so monstrous it’s unthinkable? As she unravels the truth, she discovers that the danger is closer than she ever imagined, and the man she was meant to marry might be the reason she won't survive. For fans of the chilling domestic suspense and the jaw-dropping twists…, The Stranger Upstairs is a relentless, slow-burn thriller that explores the terrifying line between love and obsession, and what do you do when the monster isn't under your bed, but lying next to you?