The Case of the Mayfair Photographer's Plate

Section I

The Scene

Hand-drawn case map for The Case of the Mayfair Photographer's Plate, showing Mr Coltsfoot's photographic studio, Mount Street, Mayfair. — The ground in question.

Setting: Mr Coltsfoot's photographic studio, Mount Street, Mayfair
Time: Saturday afternoon, second Saturday of August 1894
Weather: Warm; bright sun through the studio's high north window
Atmosphere: A long studio with a panelled screen and three velvet chairs; the photographer's plate-camera on a tripod; the smell of fixer and varnish.

Section II

The Suspects

Mr Coltsfoot

Photographer of Mount Street

A precise, well-mannered photographer of forty-five, twelve years in his Mayfair studio, with a quiet reputation for portraits of the season's principal ladies. He had photographed Mrs Avery on three sittings of an hour each on the Wednesday last.
Mrs Avery

Wealthy patron, the client

A composed, careful gentlewoman of fifty, who had commissioned the portrait at her husband's quiet expense. She had sat at the appointed sittings - by her own account; by Miss Brooke's, also her own account.
Miss Brooke

Mrs Avery's paid companion, eleven months in the household; the most vivid witness

A keen, well-dressed young woman of twenty-eight, who had been Mrs Avery's companion through the year. She had given Holmes, in the morning's interview, the most vivid account of the studio sittings - the angle of the photographer's plate, the colour of the velvet chair, the small remarks Mr Coltsfoot had made - beyond what an attendant on the stair could have known.
Mr Tarn

Rival photographer in Cork Street

A florid, prosperous photographer of fifty, who had lost the season's principal patrons to Mr Coltsfoot through the summer. He had been heard to wish him ill at his club on the Tuesday before the sittings.

Section III

The Evidence

The proof on the plate

The proof showed a woman in Mrs Avery's hair-dressing and Mrs Avery's dove-grey dress, but the face was not Mrs Avery's. There was no birthmark, no scar, no feature Mr Coltsfoot could pin a name to; he could say only that the sitter and the patron were two women, not one. Whether the sitter was a known person of the season's set or a hired look-alike, the proof on its own could not say.
Miss Brooke's vivid account

Miss Brooke's morning's account of the studio sittings included the angle of the plate-camera, the colour of the velvet chair, and three particular remarks of Mr Coltsfoot's during the third sitting which an attendant waiting on the stair could not have heard. She had not, by Mr Coltsfoot's record, been within the studio at the third sitting at all - she had waited in the receiving-room downstairs.
Mrs Avery's three sittings

The studio's appointment-book showed three sittings of an hour each on the Wednesday - at half past ten, two o'clock, and four. Mrs Avery had attended; Mr Coltsfoot had taken her plate at each. There was no record of any second sitter on those days.
Dr Sands's attendance on Mrs Avery

Dr Sands had attended Mrs Avery at her bedside on Tuesday evening - a feverish chill - and again on Thursday afternoon, finding her then much recovered. On the intervening Wednesday he had not been called. The household had told him Mrs Avery had kept to her bed through that day, but the doctor had not himself seen the patron between his Tuesday call and his Thursday return.
Mr Tarn's club-room ill-wish

Mr Tarn's club-room remark of Tuesday was loud and idle; he had not been within the Mount Street studio in eight months and had no acquaintance with Miss Brooke.

Section IV

Statements & Testimony

Mr Coltsfoot

Photographer

“"My appointment-book shows three sittings of an hour each on Wednesday, sir. The lady gave me her name as Mrs Avery; I had not photographed her before. She was elegantly turned out, in a dress of dove-grey and small jet earrings. I made the plates; I sent the proof on Friday by my boy. I have not heard of any quarrel with the studio."”
Dr Sands

Mrs Avery's family physician

“"I attended Mrs Avery on Tuesday evening, sir, with a feverish chill; I did not see her again until Thursday afternoon, when she was much recovered. On the Wednesday I was not called to the house. The household says she kept to her bed, but I cannot say so on my own evidence; I had not the sight of her that day."”

Section V

Your Verdict

Three picks render a verdict. Name the culprit, choose the method, and nail the keystone clue. We score all three — partial credit if you got the culprit but missed the method, full credit only if you got Holmes’s exact reasoning.

1. Name the culprit

Mr Coltsfoot Photographer of Mount Street Mrs Avery Wealthy patron, the client Miss Brooke Mrs Avery's paid companion, eleven months in the household; the most vivid witness Mr Tarn Rival photographer in Cork Street

2. Choose the method

Which of these accounts of the deed best matches the evidence?

Mr Coltsfoot sent a stranger's proof in place of Mrs Avery's three Wednesday plates, relying upon the dove-grey dress and small earrings to conceal his professional error. Mr Tarn paid the photographer's boy to exchange Friday's proof after his club-room ill-wish, though he had not entered the Mount Street studio himself. An unknown look-alike presented herself in Mrs Avery's dove-grey dress and jet earrings, completed the three sittings, and left the household to discover the false face. Miss Brooke impersonated Mrs Avery for the three sittings while her mistress lay ill; her vivid account places her there as a sitter.

3. Pick the keystone clue

Of all the evidence above, which single piece nails the case?

The proof on the plate Miss Brooke's vivid account Mrs Avery's three sittings Dr Sands's attendance on Mrs Avery Mr Tarn's club-room ill-wish

Choose a culprit, a method, and a keystone clue to render your verdict.