Colonel Anthony Ruthven Gethryn, that unlikely part owner of The Owl magazine, is recalled from a holiday in Spain, his mother's country, to solve a murder mystery amid London's November fogs. He finds that his wife Lucia is sheltering Mrs Bronson, whose husband is in prison awaiting the hangman's noose for the murder of a gamekeeper six months before. A petition for reprieve has been rejected and Bronson will shortly hang for someone else's crime.

Convinced by Mrs Bronson that her husband is innocent, Gethryn, aided by the staff of The Owl and by a Scotland Yard detective officially on holiday, embarks on a seemingly hopeless race against time to prove Bronson's innocence and another man's guilt before the date appointed for that last fatal 'nine o'clock walk'.

This title was first published in the Crime Club in 1930 and was the first title chosen to appear under that imprint.