The Twenty-One Clues

The constable was content to call it a suicide pact. All the evidence was there. The bodies of John Barratt and Mrs Callis were discovered in a lovers' nook among some bracken. Beside them was a pistol with Barratt's fingerprints on it, and torn up letters in the handwriting of Barratt and Mrs Callis were scattered around. Arrangements for the elopement had apparently been complete. Why had their plans fallen through? Why had they turned their backs on the railway station with tickets to London in their pockets? Sir Clinton Driffield is not so sure that the obvious solution is the right one....