The fourth film was not supposed to be the last one of the series, but Bonita Granville chose to turn to more adult roles and Warner Bros. decided not to fill her gumshoes. Her Nancy is more frenetic than ever in this episode, which is, finally, actually based on one of the Nancy Drew stories. A genuine creepiness to the mansion where the Turnbull sisters live — and must reside for two more weeks in order to ensure their ownership, and which has been bequeathed to turn the property into a children’s hospital — provides this entry with an intrigue absent from the others. The mystery itself is again rather obvious but this time things are well plotted and executed.

From the very beginning Nancy is involved in the case and she considers it her responsibility to ensure that the sisters remain in the house to fulfill their promise to donate the property later. Ted is more mature; he has taken a job as an ice deliveryman, which only makes him more valuable to the teenage sleuth, as he now provides access to places she needs to investigate. Ted continues to do her bidding, and they do have one clinch when things turn dangerous in the tunnel, but his romantic pinings for Nancy are definitely a thing of the past. Ted remains the chief source of comic relief, whether crashing backwards through a window or dressing in drag (again) because his clothes have been stolen. But he also proves his shooting prowess and once again saves Nancy at the film’s climax.

What makes this film better than the others? It marks a return to Nancy as detective. She uses Ted’s belt to determine that a death is not a suicide as believed (a belief she reinforces to keep the sisters in place), but murder. It is her plan that leads to the discovery of the hidden staircase, and the secret behind the murder. Nancy places herself (and Ted) in peril, more concerned with the situation at hand than her personal safety.