"Have you ever loved so much, you would kill?"

I run my fingers over those words. Finally, a bit of excitement on this dreary holiday. But to whom does this diary belong?

"I once loved my wife this way. If I hadn't, her first husband would be alive and they'd still be married."

How intriguing.

"She was different then. She hadn't turned into the loathsome creature I now try to avoid lying beside each night."

Can I solve this puzzle? After a week aboard the Nile Queen, I have the measure of my fellow passengers. But where to start? There's certainly no love between the major and his wife. Can this be his diary?

"She is nosey, unpleasant and downright rude."

No, the major's wife wouldn't say boo to a goose. What about the Smythe-Pearces? She's definitely cut from the right cloth.

"I have fallen for another. She is pure, sweet and kind. Everything my wife no longer is."

What an utter cad! My lips curl with glee as I turn the page.

"She is also beautiful, as my wife once was."

Mrs Smythe-Pearce may be disagreeable, but she's still attractive, so it's not them. What about the archaeologist, Sir Mallowan? He spends his time drinking and smoking, while his wife sits scribbling in that blasted notebook. Neither looks happy. Yes, they fit the bill!

"I wish to marry her, but I've become accustomed to money. This is why I must now kill again. Out of mercy, my wife will be in little pain when the poison takes effect."

How very gallant of you.

"It will seem like death by natural causes, for she'll be alone in our cabin when this occurs. I shall be up on deck, taking in the air with that charming writer, Agatha and her husband, Max Mallowan. A perfect alibi."

Not the Mallowans then?

"I've used my wife's love of a murder mystery to my advantage. And her irritating habit of licking her index finger before using it to turn a page."

I look down at my finger, still wet with spittle.

"It's already far too late, my love. I just wanted you to know, it was me."