A routine visit to an elderly relative in a nursing home spirals into a dangerous investigation when Tommy and Tuppence Beresford uncover unsettling secrets hidden within the facility. The protagonists, now older and more seasoned, must navigate the cryptic ramblings of the home's residents to determine if a series of suspicious deaths are merely coincidental or the result of calculated malice. As they peel back the layers of the gothic environment, they encounter resistance from the staff and a pervasive atmosphere of unease. The narrative unfolds through a classic third-person perspective, emphasizing the duo's sharp observational skills and their enduring partnership as they confront a threat that hints at dark, occult undertones.

This novel is often noted for its departure from the high-octane espionage of the earlier Tommy and Tuppence stories, favoring a more atmospheric and domestic mystery. Readers frequently highlight the shift in tone as the protagonists age, reflecting a more contemplative approach to their detective work. The gothic setting of the nursing home serves as a distinct backdrop that distinguishes this entry from Christie's more traditional village-based mysteries. While some critics point to the slower pace compared to her earlier works, the character dynamics remain a central point of interest for long-time fans of the series. The narrative effectively balances the mundane realities of aging with the sinister undercurrents of a classic Christie puzzle.