Murder on the Blackboard

Miss Withers finds the dead body of music teacher Louise Halloran in a schoolroom and immediately summons Inspector Oscar Piper. By the time Piper arrives, the corpse has vanished, leaving everyone baffled. She reasons that the killer must still be inside the building, since the only entrance was under surveillance.

Withers notes that the building’s only entrances were observed, so the culprit could be hiding somewhere inside. She warns Piper that a second strike could come at any moment. The investigation shifts to a claustrophobic inside-the-building pursuit.

During the search of the school, Detective Donahue is knocked unconscious in the basement, complicating the investigation. The incident proves the killer is willing to physically confront investigators. Withers doubles down on collecting clues despite the setback.

Withers discovers a clue in Halloran’s classroom—a tune chalked on the blackboard that seems to spell out a name. She suspects the tune is a coded message left by the killer. The clue deepens the mystery and ties the crime to someone connected to Halloran.

The body is later found being burned in the basement furnace, and the fire alarm sounds as the murderer makes a hasty escape. The scene suggests a staged crime and raises the stakes for the investigation. Piper and the team must rethink suspects in light of this new discovery.

Otto Schweitzer, the janitor, is arrested by Piper on suspicion of the murder due to a financial quarrel with Halloran. Withers remains unconvinced he is the real killer. The arrest shifts the focus to other potential suspects inside the school.

At Halloran’s apartment, Withers learns Halloran held one of the Irish Sweepstakes tickets, suggesting a possible financial motive. Jane Davis claims a half-share in the ticket, giving her another motive to fear for her life. The new information broadens the field of suspects.

Addison Stevens admits Halloran was attracted to him, indicating a personal motive could be involved. He hints at a complicated dynamic and a potential secret relationship. His admission adds a layer of jealousy to the investigation.

During another basement search, the lights go out and someone throws a hatchet at Miss Withers. She narrowly avoids harm, proving the killer is still dangerous and willing to use violence. The threat heightens the urgency to identify the culprit.

A fragment of a burnt love letter from Stevens to Halloran is found, confirming their past relationship. The piece provides a tangible link between him and Halloran that could explain the motive. Withers catalogs this new evidence as the case tightens around Stevens.

Donahue wakes in the hospital unable to recall what happened, and Withers has Piper tell newspapers that Donahue knows the killer’s identity. The hospital becomes a focal point for exposing the culprit. Public and press pressure intensifies the pursuit of the truth.

The killer infiltrates Donahue’s hospital room to poison his medicine, triggering a dramatic trap. The murderer is Addison Stevens, revealed through the earlier clue of the initials on the blackboard. Stevens recalls that Halloran and he were secretly married, and that his feelings grew dangerous as she refused to leave him.

Stevens drinks the poison rather than be captured, but not before exposing his motive. He explains that Halloran’s refusal to leave him pushed him to act decisively. In the aftermath, a final twist shows Detective Smiley North has been breakfasting with the pretty woman, undermining Withers’ trust and closing the circle of deceit.