Growing up, Kate Priddy was always a bit neurotic, experiencing momentary bouts of anxiety that exploded into full-blown panic attacks after an ex-boyfriend kidnapped her and nearly ended her life. When Corbin Dell, a distant cousin in Boston, suggests the two temporarily swap apartments, Kate, an art student in London, agrees, hoping that time away in a new place will help her overcome the recent wreckage of her life. But soon after her arrival at Corbin’s grand apartment on Beacon Hill, Kate makes a shocking discovery: his next-door neighbor, a young woman named Audrey Marshall, has been murdered.