This particular drama may be be a fairly easy one for you to catch because you had some preparation and the plot is somewhat plain. Nonetheless, it is a literary classic from England written in 1939! It is no surprise that certain vocabulary and ways of speaking would be tough to catch. Don't fret about what you couldn't get; celebrate what you could understand! Just think: you enjoyed an evening of English language theatre and could generally follow it. Good work and good for all of you!

OK, about the murders. Judge Wargrave was insane. In his long career, he had always wanted to be able to kill ("get justice against") certain people--that he had found out about---who had in some way directly or indirectly caused the death of someone(s) but who, for various reasons, could not be touched by the law. Anthony Marston was killed first because he had "accidently" run over two children. Mrs. Rogers (the cook) and her husband (the houseman) had "neglected" to give heart medicine to their elderly employer, who was going to leave them money in her will. General MacKenzie had deliberately sent his wife's young lover to the heart of battle, knowing that he would die there. Religious fanatic Emily Brent had very heartlessly fired her young assistant when she was found to be pregnant, and the young woman then committed suicide. Dr. Armstrong had been an alcoholic and once was drunk while operating and killed the patient (but it was kept a secret because only the nun who assisted him knew about it . . .) Wargrave was, of course, not really killed. It was a plot with Armstrong to try to find out the real murderer. After this, Wargrave pushed Armstrong off a cliff and made it look like suicide. People would believe this easily because Armstrong was so nervous! Blore had sent an innocent man to prison---where he died---in order to receive money from a gang. Lombard had indirectly caused the death of his 22 African safari members. Vera had allowed a young boy---her lover's nephew---to drown because the lover would have inherited a lot of money if the boy had not been next in line to receive it (and the lover was too poor to marry her otherwise). Ironically, the lover dropped her after this happened. Justice Wargrave had sentenced what was widely considered to be an innocent man to death, but, again ironically, it was later proven that the man, Seton, was actually guilty.
Wargrave saved Vera to the last because he thought she was the smartest and because he wanted to end it by "hanging a woman". In the book, the ending is different. No one survives and it is the "perfect crime", baffling the police until Wargrave's detailed written confession is found, included as a postscript at the end of the book.
Fun Halloween mystery, eh?
Blog on!