N or M by Agatha Christie

foolish thing to do. Movements of troops and air squadrons are just what the Germans want to know.”
    “Oh, but I never tell anyone,” cried Tuppence. “I'm very, very careful.”
    “All the same it's an unwise thing to do - and your boy will get into trouble over it some day.”
    “Oh, I do hope not. I'm his mother, you see. A mother ought to know.”
    “Indeed and I think you're right,” boomed out Mrs O'Rourke. “Wild horses wouldn't drag the information from you - we know that.”
    “Letters can be read,” said Bletchley.
    “I'm very careful never to leave letters lying about,” said Tuppence with an air of outraged dignity. “I always keep them locked up.”
    Bletchley shook his head doubtfully.

N or M
    III
    It was a grey morning with the wind blowing coldly from the sea. Tuppence was alone at the far, end of the beach.
    She took from her bag two letters that she had just called for at a small news agent's in the town.
    They had taken some time in coming since they had been readdressed there, the second time to a Mrs Spender. Tuppence liked crossing her tracks. Her children believed her to be in Cornwall with an old aunt.
    She opened the first letter.
    "Dearest Mother,
    "Lots of funny things I could tell you only I mustn't. We're putting up a good show, I think. Five German planes before breakfast is today's market quotation. Bit of a mess at the moment and all that, but we'll get there all right in the end.
    "It's the way they machine gun the poor civilian devils on the roads that gets me. It makes us all see red. Gus and Trundles want to be remembered to you. They're still going strong.
    "Don't worry about me. I'm all right. Wouldn't have missed this show for the world. Love to old Carrot Top - have the W.O. given him a job yet?
    "Yours ever,
    “Derek.”
    Tuppence's eyes were very bright and shining as she read and re-read this.
    Then she opened the other letter.
    "Dearest Mum,
    "How's old Aunt Gracie? Going strong? I think you're wonderful to stick it. I couldn't. No news. My job's very interesting, but so hush-hush I can't tell you about it. But I really do feel I'm doing something worth while. Don't fret about not getting any war work to do - it's so silly all these elderly women rushing about wanting to do things. They only really want people who are young and efficient. I wonder how Carrots is getting on at his job up in Scotland? Just filling up forms, I suppose. Still he'll be happy to feel he is doing something.
    "Lots of love,
    “Deborah.”
    Tuppence smiled.
    She folded the letters, smoothed them lovingly, and then under the shelter of a breakwater she struck a match and set them on fire. She waited until they were reduced to ashes.
    Taking out her fountain pen and a small writing-pad she wrote rapidly.
    "Langherne, Cornwall.
    "Dearest Deb,
    "It seems so remote from the war here that I can hardly believe there is a war going on. Very glad to get your letter and know that your work is interesting.
    "Aunt Gracie has grown much more feeble and very hazy in her mind. I think she is glad to have me here. She talks a good deal about the old days and sometimes, I think, confuses me with my own mother. They are growing more vegetables than usual - have turned the rose garden into potatoes. I help old Sikes a bit. It makes me feel I am doing something in the war. Your father seems a bit disgruntled, but I think, as you say, he too is glad to be doing something.
    "Love from your
    “Tuppenny Mother.”
    She took a fresh sheet.
    "Darling Derek,
    "A great comfort to get your letter. Send field postcards often if you haven't time to write.
    "I've come down to be with Aunt Gracie a bit. She is feeble. She will talk of you as if you're seven and gave me ten shillings yesterday to send you as a tip.
    "I'm still on the shelf and nobody wants my invaluable services! Extraordinary! Your father, as I told you, has got a job in the Ministry of Requirements. He is up north somewhere. Better than nothing, but not