John Minute, formerly an unscrupulous African mining magnate, has flown to England, but can’t escape his past. Constantly threatened by blackmailers, he fears death and financial ruin. At the suggestion of the commissioner of police, “The Man Who Knows” is hired to assist in determining the source of these threats.

But after John is murdered, suspicion is cast on his nephew, who calls on The Man Who Knows to help clear his name and cast suspicion on Jasper Cole, John’s loyal secretary. The trail to the real murderer presents a formidable challenge—even to The Man Who Knows.

Published in 1918, The Man Who Knew was adapted for film in 1961.