Zane Kane is the private secretary to David Ellsworth, the multimillionaire, ruby collector, and noted philanthropist. Part of Billy’s job is vetting the stories of all the poor people who appeal to Ellsworth for help. Those who tell the truth are handsomely rewarded, and those that are running a con are turned out. It’s a job that quickly familiarizes Billy to New York’s underworld and the people who haunt it.
Late one evening, Billy discovers that his boss has been murdered and the rubies stolen. It’s clear that whoever committed the crime intended for Billy to take the wrap, as all the evidence left points conclusively to him. Pursued by the police, Billy escapes into the underworld, where he finds himself mistaken for a gangster known as the Rat. The resemblance must be uncanny, as no one so much as doubts that the Rat is back in town.
Billy intends to use the new persona as a cover to search for Ellsworth’s real killer, who he eventually identifies as the Man with the Crutch, but the appearance of the Woman in Black complicates matters. The Woman in Black is holding something over the Rat — what, Billy doesn’t know, but evidently it’s enough put him in her power. She directs hims to thwart all his gang’s criminal activities, which he does by adopting a third persona. All of them are dangerous: Billy Kane is hunted by the police, the Man in the Mask is hunted by the underworld, and the Rat will be in a sticky situation should the actual Rat ever return.
Speaking of that, where is the Rat and how is it that his impersonator has gone unnoticed so long? As it turns out, he’s never been away at all — the Rat and the Man with the Crutch are one and the same — and he’s well aware of Billy’s activities — in fact, he’s setting Billy up to take another fall. He intends on killing the troublesome Woman in Black, after which her securities against him will be made public, but that matters little, because “the Rat” will also be found dead.
Interesting tidbit, Doors of the Night contains one of the earliest usages of “– not!” I’ve seen. There are earlier, some dating back to the 19th century, but they’re uncommon and don’t read exactly like the familiar 1990s catchphrase, which this one absolutely does:
The Cherub, a young thug with a disarmingly innocent face, is talking to Shaky Liz, a disheveled, elderly boozehound. He was speaking about his grandmother when he tells her:
“She looked just like youse, too — not!”
Shaky Liz scowled.
(Packard, 1922, p. 264)