The young doctor. Conan Doyle on his graduation from medical school, 1881

ARTHUR CONAN DOYLE COLLECTION—LANCELYN GREEN BEQUEST, PORTSMOUTH CITY COUNCIL

The young doctor. Conan Doyle on his graduation from medical school, 1881

Conan Doyle’s medical-school teacher Dr. Joseph Bell, whose diagnostic powers seemed to verge on sorcery. He was the real-life model for Sherlock Holmes.

ARTHUR CONAN DOYLE COLLECTION—LANCELYN GREEN BEQUEST, PORTSMOUTH CITY COUNCIL

Conan Doyle’s medical-school teacher Dr. Joseph Bell, whose diagnostic powers seemed to verge on sorcery. He was the real-life model for Sherlock Holmes.

The Anglo-Indian lawyer George Edalji. Investigating his wrongful conviction marked Conan Doyle’s first extended involvement in a real-life case.

ARTHUR CONAN DOYLE COLLECTION—LANCELYN GREEN BEQUEST, PORTSMOUTH CITY COUNCIL

The Anglo-Indian lawyer George Edalji. Investigating his wrongful conviction marked Conan Doyle’s first extended involvement in a real-life case.

This secret message, carried to Conan Doyle in the mouth of a paroled convict in 1925, would bring about Slater’s release.

GLASGOW CITY COUNCIL: ARCHIVES; TD1560/1/1.

This secret message, carried to Conan Doyle in the mouth of a paroled convict in 1925, would bring about Slater’s release.

The Glasgow police detective John Thomson Trench sacrificed his career after voicing doubts about the Slater case.

PETERHEAD PRISON MUSEUM

The Glasgow police detective John Thomson Trench sacrificed his career after voicing doubts about the Slater case.

Conan Doyle and (part of) Windlesham, his vast home in southeast England

ARTHUR CONAN DOYLE COLLECTION—LANCELYN GREEN BEQUEST, PORTSMOUTH CITY COUNCIL

Conan Doyle and (part of) Windlesham, his vast home in southeast England

Conan Doyle with Craigie Aitchison, now regarded as the greatest Scottish criminal lawyer of all time, at the review of Slater’s case in 1928

ARTHUR CONAN DOYLE COLLECTION—LANCELYN GREEN BEQUEST, PORTSMOUTH CITY COUNCIL

Conan Doyle with Craigie Aitchison, now regarded as the greatest Scottish criminal lawyer of all time, at the review of Slater’s case in 1928

Mary Barrowman in the late 1920s, around the time of Slater’s release. “She is in the streets & has been in prison,” one Scottish journalist discovered.

PETERHEAD PRISON MUSEUM

Mary Barrowman in the late 1920s, around the time of Slater’s release. “She is in the streets & has been in prison,” one Scottish journalist discovered.

Dapper again: A post-release Oscar Slater, late 1920s

WILLIAM ROUGHEAD, TRIAL OF OSCAR SLATER (1950)

Dapper again: A post-release Oscar Slater, late 1920s