Title: The Mark of the Bat
Air date: July 24, 1938
Plot summary: A rich explorer named Stevens dies, of some sort of strange anemia. His daughter Claire, heir to his huge fortune, is very sick, with a strangely similar anemia. In other news, Stevens's stepson Dr. Vickers, who was treating him, seems oddly unconcerned. Also, it so happens that Mr. Stevens was also an enthusiast of vampire bats and bred them on his property, and his bats have been biting and killing local livestock.
Lamont Cranston, who knew Stevens, reads the obituary and smells a rat. He and Margo come to visit but as they approach the mansion they find Claire's fiancée, David Henderson, collapsed by the side of the road—with a vampire bat sucking on his neck.
Tropes:
- Animal Assassin: Dr. Vickers has trained the bats to attack people and suck their blood until they die of anemia.
- As You Know: A lot of this in the opening scene as the two servants at the Stevens house talk about how Mr. Stevens is on the verge of death and Claire is also sick, and it's probably because of those creepy bats.
- "Be Quiet!" Nudge: The Shadow has to punch David Henderson out in order to stop him from charging in unprepared and getting killed by Dr. Vickers.
- Bloodsucking Bats: Stevens bred unusually aggressive vampire bats that can attack people and, in groups, drain them dry of blood.
- Driven to Suicide: Dr. Vickers goes plunging into the bat cave, to his death, after realizing that the jig is up.
- Inheritance Murder: The ultimate motive. Dr. Vickers wants to get his hands on the Stevens fortune.
- Title Drop: Lamont says "there will be no more marks of the bat" at the end of the episode, as he tells Margo how he killed all the bats with dynamite.
- Wolves Always Howl at the Moon: The script specifies dogs, not wolves, but the effect is basically the same, as the howling dogs add to the spookiness around the Stevens mansion.
