The Tragedy of X

In the early 1930s, within the bustling streets of New York City, a man falls victim to poisoning while aboard a crowded streetcar during the chaotic rush hour. Longstreet's demise is witnessed by all aboard, yet the perpetrator remains invisible to everyone. Inspector Thumm is left with only a handful of cryptic clues, each leading to a dead end. Frustrated by the lack of progress, he ultimately turns to Drury Lane, a retired Shakespearean actor, master of disguise, and amateur detective.
Drury Lane, ensconced within the grandeur of his expansive medieval castle along the Hudson River, listens intently as the inspector recounts the perplexing case. Instantly, he discerns the identity of the murderer but withholds this revelation until he gathers sufficient evidence to assist the police in making an arrest.