Lucy: This time her closed circle would be a luxurious paddle steamer on the Nile.

Agatha and Max boarded this very boat in 1933.

The SS Sudan was built in 1885 for Egypt's royal family, and later converted into a cruise ship for wealthy tourists.

On the surface, "Death on the Nile" is classic Christie.

A rich cast of characters is trapped on the boat, and when a murder occurs, Hercule Poirot is onboard to solve the case.

But it's more than that.

In this book, Agatha uses her own observations of love, marriage, and betrayal as the engine of the story.

I've been reading the book again, and I've noticed it's also got another one of Agatha's favourite devices in it-- the hidden couple.

To explain how this works, I'm going to have to do a bit of plot spoiling.

The story starts with Jackie and Simon who are in love.

But they're very poor.

Jackie has a plan though.

She asks her friend Linnet, a rich American, to give Simon a job.

Linnet says, "Absolutely."

Everything is going very well.

Fast forward three months, and Simon, the cad, he leaves Jackie and goes off with rich Linnet instead.

They get married.

They go on their honeymoon to Egypt.

But who should turn up like the ghost at the feast?

It's the jilted, troubled Jackie who follows in their footsteps.

Everywhere they go, she seems to be there, too.

There's definitely going to be trouble.