Halfway through the book, when the twin sister is introduced, the solution becomes intuitively apparent. Since every Christie that I had read before always brought up an ingenious solution, I dismissed it, thinking that it couldn't be this obvious.
Unfortunately, it came out to be true, and that's the worst thing I can say about a Christie novel. The way it was structured and the stodgy dialogue pretty much gave the mystery away quite some time before the conclusion. You could extract a soap drama from the melodramatic ‘reveal' which felt cheesy enough to be used for a Margherita pizza.
Elephants can remember but this was a forgettable book.