[2][1] He was the son of Margaret (née Johnston) and Isaac Henderson (1814–1884), co-owner of the New York Evening Post with William Cullen Bryant and John Bigelow.

[3][2] His father's career at the Post ended in 1878 when an investigation revealed he had defrauded Bryant for thirty years.

[2][7] He attended Williams College, graduating with a bachelor's degree, Master of Arts, and Doctor of Civil Law.

[14] The Boston Gazette noted, "The book is admirably written, and its heroine, an exceptionally attractive character, is drawn with great skill and force.

"[13] The Chicago Times wrote, "She is a creature of such perfect individuality, such strength of character and beauty of soul, that her creation must attain importance in American fiction.

[13] In 1892, Sir Charles Wyndham produced Agatha Page as the play The Silent Battle at the Criterion Theatre in London, England.

The Washington Herald noted, "If he had been a poor man, Mr. Henderson would doubtless have been a prolific writer, but his modest fortune was abundant for his needs, and he wrote but little.

"[14] Henderson married Marion Temple Brown on February 13, 1880, at the Madison Square Presbyterian Church.

[11] In 1888, he had moved back to London, living South Kensington in an exclusive neighborhood, The Boltons.