Inspector French

I: Mr. Morgan Meets Tragedy

Scotland Yard detective summoned to investigate the case; travels west by train.

II: Inspector French Gets Busy

Arrives from London to lead the investigation; examines the body and crate; discusses the case with Sergeant Nield.

III: Experimental Detection

Leads the investigation, theorizes about the lorry and crane, interviews Tom Manners, and plans to trace the crane-lorry.

IV: A Change of Venue

French shifts his focus to Swansea and Ashburton, coordinates with Superintendent Howells, and plans to trace the lorry and investigate the duplicating machine order.

V: Messrs. Berlyn and Pyke

Arrives in Ashburton, investigates the crate and the disappearance of Berlyn and Pyke, interviews Sergeant Daw and Mr. Fogden.

The Despatch of the Crate

Conducts detailed investigation at Veda Works, interviews witnesses, and reviews despatch records.

Dartmoor

Consults Sergeant Daw, investigates the car and the moor, tests the breakdown theory.

VIII: A Fresh Start

Conducts interviews with Lizzie Johnston and Sergeant Daw, tests the sock clue, and refines his theory about the murder.

IX: A Step Forward

Interviews Jefferson Pyke and the landlady; deduces the body is Stanley Pyke's and suspects Berlyn.

X: London’s Further Contribution

Conducts interviews in London, first with Mrs. Berlyn and then with Mr. Illingworth; struggles with contradictory evidence about the car's breakdown.

XI: John Gurney, Night Watchman

French deduces Gurney must know something about the night the body was placed in the crate, visits him at home, and uses a combination of friendly conversation and direct questioning to extract information.

XII: The Duplicator

Continues his investigation, interviews Fogden and Beer, and re-evaluates the case.

XIII: The Accomplice?

Develops a new theory implicating Colonel Domlio as the accomplice; interviews Sergeant Daw, visits Domlio's house, and later returns to confront the butler Burt.

XIV: French Turns Fisherman

Confronts Colonel Domlio, investigates the well at Torview, and recovers a coat from the water.

Blackmail

Leads the investigation, confronts Domlio, and arranges to pump the well.

Certainty at Last

Reevaluates the case, interviews the Lancasters, traces the bicycle, and plans to confront Mrs. Berlyn in London.

XVII: “Danger!”

Leads the investigation, bluffs Mrs. Berlyn, intercepts a note, and develops a new theory implicating Mrs. Berlyn and Jefferson Pyke.

XVIII: On Hampstead Heath

French pursues Pyke and Mrs. Berlyn, overhears their conversation on Hampstead Heath, and reconsiders Domlio's guilt.

XIX: The Bitterness of Death

Leads the investigation, mobilizes the C.I.D., interviews witnesses, and traces Pyke to Victory Place.

XX: Conclusion

Recovers from being knocked unconscious, apprehends the criminals, and realizes his mistake in accepting the identification of the remains.