Spots 
Monte Field attends a performance of the hit play Gunplay at New York's Roman Theatre. During a tense scene in the darkened auditorium, Field collapses in his seat from fatal poisoning. Inspector Richard Queen arrives to lock down the building before any audience member can leave.
A thorough search of the victim reveals that his silk top hat has completely disappeared. Every exit was guarded, yet no audience member or staff member carries the missing headwear. Ellery Queen recognizes that removing an ordinary hat from a crime scene points to a specific, hidden motive.
Investigation into Monte Field's legal practice reveals an extensive network of extortion and bribery. Numerous prominent figures had motives to silence him and reclaim stolen documents. The hidden papers provide a long list of suspects, but do not immediately explain the physical disappearance of the hat.
Ellery Queen analyzes the physical dimensions of hats and heads to isolate the murderer. The killer took Field's top hat because the killer had to wear a hat out of the theatre and could not wear their own without revealing key evidence inside it. Deductive logic eliminates impossible scenarios until only one person fits every physical constraint.
A crooked lawyer is murdered in a crowded theater, leaving behind a clue in a missing top hat.