Black Coffee is a 1930 stage play by Agatha Christie.
It takes place at the mansion of Sir Claud Amory, in a suburb of London. It seems that Sir Claud, a physicist, has invented a formula for an explosive of incredible power. One evening Sir Claud assembles together his family and guests, and dramatically announces that the formula has been stolen! He has summoned none other than Hercule Poirot to discover the culprit. Poirot is on his way, but in the meantime, Sir Claud has his butler turn out the lights, offering the thief two minutes of darkness in which to return the formula. When the lights are turned back on, however, the formula is still missing, and Sir Claud is dead, poisoned by an overdose of sedatives in the coffee he was drinking.
So Poirot, who shows up soon after this, has to investigate a murder as well as a theft. His suspects include Sir Claud's sister Aunt Caroline, Sir Claud's debt-ridden son Richard, Richard's half-Italian wife Lucia (who has a troubled past), Sir Claud's hard-partying niece Barbara, Sir Claud's assistant Edward Raynor, and Dr. Carelli, a suspicious Italian fellow who knows Lucia and supposedly met her again by accident that very day.
Agatha Christie had a busy secondary career as a playwright, most famously with The Mousetrap, but this is the only Hercule Poirot story written originally for the stage. The Christie estate licensed a novel version by Charles Osborne that was published in 1998; this trope list is based on the original play.
Tropes:
- Absence of Evidence: The lack of dust on the box of poisons, when everything else on the bookshelf was covered in dust, leads Poirot to conclude that someone had accessed the poison well in advance.
- Applied Phlebotinum: Sir Claud has invented "amorite", a new explosive with a destructive power orders of magnitude greater than conventional explosives. (Agatha Christie in this 1930 play managed to anticipate that "atomic research" might result in a phenomenally powerful explosive.)
- Asshole Victim: Barbara, who is not one for the usual social niceties, says that Sir Claud was a domineering miser and that to some extent everyone's glad he's dead.
- As You Know: In the opening scene Aunt Caroline makes sure to mention for the audience that Lucia is from Italy and Dr. Carelli is her "Italian friend."
- Blackmail: It turns out that Lucia is the daughter of a recently deceased Honey Pot Italian spy. Dr. Carelli knows this, has been blackmailing her, and had hoped to blackmail her into getting him the secret formula. (This is a very rare example in the Christie canon where a blackmailer isn't punished by death, but is merely arrested.)
- Bluffing the Murderer: Poirot gets Raynor to confess by pretending to drink the drugged drink that Raynor gave him. What Raynor doesn't know is that Captain Hastings switched out the glasses when Poirot temporarily got Raynor out of the room.
- Chekhov's Gun: The tapers, and how Poirot with his compulsion for neatness finds himself rearranging them when they're disturbed. After he has to do this a second time he realizes that someone has messed with them. The formula is hidden inside one of them.
- Ill-Timed Sneeze: Hastings's sneeze when he and Poirot are hiding behind the French window reveals their presence to Barbara as she's reaching for the poison box.
- I Need a Freaking Drink: Done on someone else's behalf. After everyone observes Lucia's emotional agitation and how she nearly fainted, Barbara says "I think she needs a good stiff drink," and recommends a strong cocktail (but does not actually get one for her).
- Lights Off, Somebody Dies: Sir Claud orders his butler to turn out the lights in order to give the thief two minutes to return the formula. Instead, when the lights come back on, an empty envelope has been left on the table and Sir Claud is dead in his chair. Partially subverted, as Sir Claud was killed by a poisoned cup of coffee that he drank just before the lights went out.
- Literal Metaphor: As they inspect the room, Hastings says Poirot can't fool him, saying "You can't throw dust in my eyes." Poirot immediately sweeps his hand across the dusty bookshelf and literally throws dust in Hastings's eyes.Poirot: It seems, my friend, that is just what I have done.
- MacGuffin: "Amorite", the explosive invented by Sir Claud. His formula is the motive for theft and eventually murder.
- Maiden Aunt: Aunt Caroline, Sir Claud's fussy sister who exists to provide some comedy with all her complaining about how young people drink too much and are too sexually liberated.
- Poisoned Chalice Switcheroo: Averted. Lucia is shown dumping a bunch of hyocine in her cup and it's implied that her cup was switched out with Sir Claud's, but it's eventually revealed that the killer independently slipped the drug into Sir Claud's cup.
- Repeat After Me: Poirot has Aunt Caroline close her eyes in an attempt to remember what she heard when the lights went out. He tells her to "throw yourself back" and she literally throws herself back in the chair, forcing Poirot to say "No no, throw your mind back."
- Tampering with Food and Drink: Sir Claud is killed by an overdose of the powerful sedative hyoscine, slipped into his coffee.
- Unable to Support a Wife: Richard went ahead and got married to Lucia anyway, but his broke-ness forces them to live with Sir Claud. Richard hates living under the thumb of his domineering father.
- The Watson: Captain Hastings, Poirot's sidekick who is always there to make Poirot look brilliant by being decidedly not brilliant in comparison. Lampshaded when Poirot is asking if Hastings understands what he's getting at by saying the murder was planned in advance, and Hastings saying "No, you know I never see these things."
