The calm of a quiet Hampstead street is shattered one summer morning, when Mr. and Mrs. Mason are found stabbed to death. Apparently victims of a savage revenge killing, the words 'blackmailer' and 'murderer' have been tattooed into the dead couple's foreheads, along with nine downward strokes with a line running through them - a cancelled score, to symbolise the one now brutally settled.
Inspector Barrin is convinced that the culprits are to be found amongst the occupants of an adjacent boarding house, one of whom is romantically involved with the Masons' ward. Barrin finds help from an unexpected quarter Kate Clare and Tony Marsh, two journalists who hold an important clue to the Masons' nefarious past. Together the three set out to solve the conundrum of the Masons' death - but with a ruthless killer on the loose, no one is safe...
Originally published in 1929, this is a classic British murder mystery from the golden age of crime fiction.