Chloral hydrate
Chloral hydrate is a sedative and hypnotic drug that plays a central role in the sequence of murders on Indian Island. It is the substance Lawrence John Wargrave uses to kill Ethel Rogers and to render Emily Brent helpless before her death, and its presence in the judge's own medical supplies makes him the only person who could have administered it without immediate suspicion. The drug's unobtrusive nature—it can be slipped into a drink or taken as a sleeping draught without the victim's knowledge—makes it an ideal weapon for a murderer who needs to kill without noise or struggle, and its use in two of the ten deaths ties the chemical directly to the pattern of the nursery rhyme that governs the killings.
Nature and Origin
Chloral hydrate is a sedative-hypnotic compound that was commonly prescribed for insomnia in the early twentieth century. Wargrave obtains it legitimately: during recent bouts of pain, his doctor prescribes him a sleeping draught containing chloral hydrate, and he suppresses the medication until he has accumulated a lethal amount in his possession. The drug is therefore part of the judge's own medical kit, not something he needs to acquire secretly or smuggle onto the island. This fact is crucial to the plot because it means that when the survivors later search each other's rooms for weapons and poisons, Wargrave has already used up his supply and can truthfully claim to have no dangerous substances left. The drug's medical legitimacy also explains why no one suspects the judge: he is an elderly man with a genuine need for sleep aids, and the presence of a sleeping draught in his luggage seems entirely natural.
Use in the Murders
Wargrave deploys chloral hydrate twice during the killings. The first victim is Ethel Rogers. After the gramophone accusation, when Rogers brings up a glass of brandy for his wife, he sets it down on a table. Wargrave, passing that table, puts the chloral hydrate into the brandy. The drug is tasteless and odorless when dissolved in alcohol, so Mrs. Rogers drinks it without noticing anything wrong. She dies in her sleep that night, and the doctor, Edward George Armstrong, initially attributes her death to natural causes or shock. The second use comes on the morning of August 10th. At breakfast, Wargrave refills Emily Brent's coffee cup and slips his last dose of chloral into it. She becomes drowsy and giddy shortly afterward, and when the others leave her alone in the dining-room, she is nearly unconscious. Wargrave then enters the room and injects a strong solution of cyanide into her neck with a hypodermic syringe. The chloral hydrate ensures that she offers no resistance and feels no pain; it also means that when the others find her body, they see only the mark of the syringe and the signs of cyanide poisoning, with no reason to suspect that a sedative was involved.
Consequences and Aftermath
The use of chloral hydrate has two important consequences for the plot. First, it creates a false trail: because Mrs. Rogers dies in her sleep and Emily Brent is found with a hypodermic mark, the survivors naturally suspect Armstrong, the only doctor present, of having administered a fatal overdose or injection. The drug's presence in Wargrave's possession is never discovered because he uses it all before the search of personal effects takes place. Second, the chloral hydrate murders follow the pattern of the nursery rhyme: Mrs. Rogers "oversleeps herself" (the second verse), and Emily Brent is stung by a "bumblebee" (the sixth verse), though the actual cause of death is the cyanide injection. The drug thus serves both as a practical murder weapon and as a piece of the theatrical staging that Wargrave has designed. After the killings, the chloral hydrate is gone, and Wargrave has no further need of it; he completes the remaining murders with a revolver, a marble clock, and a rope, leaving the sedative as a hidden tool that the police never trace.
