Lock Every Door is a tense psychological thriller set inside a mysterious and ominous luxury apartment building with a dark past. Jules Larsen, desperate for money, accepts a high-paying job as an apartment sitter at the Bartholomew, where strict rules govern every tenant—especially the command to lock every door at all times. As fellow sitters begin to vanish and strange warnings surface, Jules realizes the building is hiding terrifying secrets. With danger closing in and no one to trust, she must uncover the truth before she becomes the next victim. Riley Sager expertly builds suspense through isolation, paranoia, and shocking revelations. Fast-paced, atmospheric, and twist-filled, this novel is perfect for readers who love claustrophobic thrillers with a sinister edge.