Dark dealings over a vast inheritance attract the attentions of mobsmen. The Shadow springs into action to defend Carter Boswick from the fell blows of Hub Rowley and his minions. The action moves from the casinos of Havana to the Upper Peninsula of Michigan as the parties chase fabulous wealth.
- Abandoned Mine: The climax takes place in one, a disused galena mine in upper Michigan. A small part of the inheritance ends up being the full ownership of the mine, though the stocks in it are worthless.
- Amoral Attorney: Farland Tracy ends up being one.
- Bold Explorer: Carter Boswick fills the bill.
- Dressing as the Enemy: The Shadow dresses up as one of Stacks Lodi's hired guns to foil an attempt on Carter's life on board the SS Southern Star.
- Dungeon Crawling: OK, Mine crawling, but since there's treasure to find and mooks to kill, the concept is pretty much the same.
- Game Between Heirs: Although it ends up more a case of "Game between heir and those who want to steal the inheritance." Houston Boswick was justifiably concerned that the vast wealth he'd hidden in the mine might be raided, and so left a cryptic clue to his heir as to the location of the coordinates of the treasure, leavingit for Carter to then search the area for its exact location.
- Gory Discretion Shot: Gibson uses this somewhat by not dwelling overmuch on the mangling of the gangsters by the out-of-control mine cars.
- I Surrender, Suckers: Farland Tracy tries this on The Shadow. It's the last mistake he ever made.
- Inadequate Inheritor: Drew Westling is thought this by Houston Boswick, and so Houston hopes that his real son returns alive to inherit, due to Drew's feckless and wastrel ways that inadvertently sets the plot by Hub Rowley to steal the inheritance in motion. Even then, Houston had provided a comfortable pension for him. In the end, Drew turns out to be worthy of a full share as he risks his life to set things right.
- Indy Escape: Or at least attempted Indy Escape... mooks just aren't good at outrunning mine carts.
- The Mole: Farland Tracy, as well as the Boswick family's butler are actually partners with Hub Rowley. Drew appears to be one, but he's actually working on his own to recover the treasure on Carter's behalf before the thugs can get it.
- Nice Job Breaking It, Hero: None of this would have happened if Drew had not gotten deep into debt to Hub Rowley. Drew had asked Farland Tracy to help him get out from under the IO Us. Instead, Tracy, believing that Drew would be the likely heir, decided to join in on Hub's plan to milk Drew for all he was about to be worth.
- Of all people, The Shadow himself has one of these, as the trail he blazed to the mine for Harry Vincent and Carter Boswick was found by Hub's goons.
- Rollercoaster Mine: Stacks Lodi and his gangsters are on the losing end of one of these, as The Shadow pushes an abandoned mine-cart train full of ore in their direction.
- Secret Path: A hidden trail leading up to the hidden mine entrance.
- Secret Underground Passage: Averted. A shaft outside the cabin that Harry and Carter are staying in is not a secret passage, but an early attempt at sinking a mine shaft that didn't pan out.
- Where There's a Will, There's a Sticky Note: Houston Boswick's will is not in the form of an actual will, but instead of two letters, one to Carter, the other to Drew, both virtually identical in content, with one to be delivered and the other destroyed.
