"It really began on January 14. It says so in the diary I kept. Thank goodness I did keep it - it's the only proper record of that horrible time, the time that Great Aunt Emma arrived. No one in the family had ever heard of her, of course, but there she was, large as life, with her veil and gloves and French cigarettes and her everlasting dear-old-lady smile. That smile. We called her Grinny because of it. And that
chitter-chattering language she used when she spoke to things OUT THERE..."

Tim and Beth have never heard of their Great Aunt Emma before, so they're surprised when she suddenly appears, grinning on their doorstep. She appears to be staying indefinitely, but their parents accept her completely and seem hypnotised by her. Soon the children make a horrifying discovery: this old woman is as dangerous as a time-bomb and she has a fearful task to perform.

Nicholas Fisk's classic story of invasion by an alien into an ordinary family home is still as chilling as when it was first written.