Helen Lambie in 1909. “This woman,” one of Slater’s supporters declared, “holds the secret.”

GLASGOW CITY COUNCIL: ARCHIVES; TD1560/6/23

Helen Lambie in 1909. “This woman,” one of Slater’s supporters declared, “holds the secret.”

This torn paper wrapper, addressed “Oscar Slater, Esq., c/o A. Anderson,” first put the police on Slater’s trail.

NATIONAL RECORDS OF SCOTLAND, JC34/1/32/12

This torn paper wrapper, addressed “Oscar Slater, Esq., c/o A. Anderson,” first put the police on Slater’s trail.

Hotel register signed on the penultimate line “Oscar Slater, Glasgow”

NATIONAL RECORDS OF SCOTLAND, JC34/1/32/43

Hotel register signed on the penultimate line “Oscar Slater, Glasgow”

Slater’s 1909 letter from the Tombs in New York to a Glasgow friend, Hugh Cameron. Cameron immediately showed this letter to the police.

NATIONAL RECORDS OF SCOTLAND JC34/1/32/16

Slater’s 1909 letter from the Tombs in New York to a Glasgow friend, Hugh Cameron. Cameron immediately showed this letter to the police.

Mary Barrowman, with her parents, arrives to testify at Slater’s trial.

© CSG CIC GLASGOW MUSEUMS AND LIBRARIES COLLECTION: THE MITCHELL LIBRARY, SPECIAL COLLECTIONS

Mary Barrowman, with her parents, arrives to testify at Slater’s trial.

The trial of Oscar Slater. Slater is visible seated in the dock, just left of center, between two policemen.

WILLIAM ROUGHEAD, TRIAL OF OSCAR SLATER (1910)

The trial of Oscar Slater. Slater is visible seated in the dock, just left of center, between two policemen.

Warders’ log, Duke Street Prison, Glasgow, 1909, shortly after Slater had been sentenced to death. “He appeared to be very upset and he made the remark wishing he was dead,” an entry from May 7 reads.

NATIONAL RECORDS OF SCOTLAND, HH12/11

Warders’ log, Duke Street Prison, Glasgow, 1909, shortly after Slater had been sentenced to death. “He appeared to be very upset and he made the remark wishing he was dead,” an entry from May 7 reads.

Under guard, a work party leaves Peterhead Prison, mid-1930s.

PETERHEAD PRISON MUSEUM

Under guard, a work party leaves Peterhead Prison, mid-1930s.

The prison train hauled granite, hewn by convicts, from a nearby quarry.

PETERHEAD PRISON MUSEUM

The prison train hauled granite, hewn by convicts, from a nearby quarry.

Before and after: Oscar Slater (top) on his admission to Peterhead Prison in 1909 and (bottom) on his release in 1927

BOTH: NATIONAL RECORDS OF SCOTLAND, HH15/20/1/6

Before and after: Oscar Slater (top) on his admission to Peterhead Prison in 1909 and (bottom) on his release in 1927

Arthur Conan Doyle with his father, Charles Altamont Doyle, 1860s

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

Arthur Conan Doyle with his father, Charles Altamont Doyle, 1860s